I got hold of a Wizards of the Coast - Eberron Pre-Production Style Guide (circa 2002-2003) Check out the evolution of the setting!

Cover Page. Most of the art is by Steve Prescott or Mark Tedin.

Ironwood is heavily present in Eberron, numerous constructs and Warforged having it incorporated into their construction, and usage as weapons all over the place, but nothing that made it iconic of the Aereni.

It's interesting to see the first versions of the Aereni trend to incorporate the death/undying iconography and appearance traits into their fashion and regalia.

No trace of 'monkey wrangler' I could find anywhere. The first element I found that never made it to the published Campaign Setting, or later versions.

There are design elements here that were later incorporated into the Valenar Elves culture as well, from art we saw of their own cities.

"Soulstripper Streetlamps" Metal AF, but again, no references to it anywhere else. Oh hey look, bodies. Are they dead? This is Aerenal, who knows? Maybe only /mostly/ dead.

Humans, but definitely ethnically distinct from most of the ones we ended up seeing across Khorvaire, but less far from what we see of the Lhazaar Principalities.

Sadly, this one was washed out in the copy I got hold of. Not sure if this is for the benefit of Seren sailors, or dragons navigating supernatural weather under their own power.

Those two little specks at the base of the stairs are humanoids, assuming this was what became the Observatory of Tyrass, which is largely helmed by a Very Old Gold Dragon scholar. (CR 28, with 6 levels in Loremaster, making him one of the heaviest of hitters in the setting if he ever chose to enter the fray.)

"Ashbound" is most closely associated with Druids, but the lore that made it to print also mentions Rangers and Barbarians. Rangers might have originally been meant to have a larger presence.

Not much change here from what made it to print.

Again, some ethnic markers.

No cross reference anywhere with Batkin, let alone their friends (goblinoids?), so they might have turned into a Shifter variant. Somewhat similar but much bulkier Desmodu showed up early 3e, and have surfaced as homebrew for 5e.

ETA:
"The batkin we have example in the old Art Achive on the Wizards' site that Nycter were originially going to be in Sharn: City if Towers. There are a few images in the Archive, like the horrid wolf, that were left on the cutting room floor and never made it into supplements and sourcebooks." - Jarrod Taylor

That is a lot of traps. No references, so who knows? Could be a tourist attraction/adventurer challenge in Sharn, an extreme security option for Kundarak banks or Dreadhold.

Look how tiny (presumably) Jaela is compared to her guards. (:

Very interesting organic structure elements. Maybe something from Arawai's agriculture aspect.

Scenic Riedra.

One of several otherwise blank pages that didn't get completed.

Later purposed into the Creation Forges. The 'artifact' part might have turned into Schema, which originated in the Age of Giants in published lore. Runic installations that allowed the casting of spells or crafting of magic items 1/day /without/ expending XP or material components. In 3.5, that was a big deal.

Style tweak to "Mournlands".

Style tweak to "Darguun".

Cliff dwelling? That's new-ish. Definitely an outlier element in anything that actually made it to print.

The best Xen'drik has to offer.

Obvious precursors to Dragonmarks.

And more of the same.

Dragon Hall could be a hall for dragons, or a hall about dragons. Note the 'glyph' inclusions.

Early elements, before they got to the below, near-surface, and falling from the sky division of Khyber, Eberron, and Siberys shards.

Argonnessen elements.

Argonnessen elements.

Symbol on the shield might be a precursor to the Sovereign Host's symbol.

Possibly linked to the "Armored Eel Fish" in Monster Manual III.

Early holy symbol, details about scarification rituals.

One of the very few full color pieces in the guide, upgraded to detailed color by Steve Prescott later on, as just an example of the Reeches, no mention of what a starmap is.

One of the iconic pieces of magitech for the setting.

Later turned into the Elemental Galleons.

https://static.wikia.nocookie.net/eberron/images/d/d0/Emerald_claw.png/revision/latest?cb=20131113193210

Easy to see the foundation this laid for a later piece of published art. The emblem seems to have been nailed down early on.

Best guess is that this evolved into Fairhold, the 'city within the city' at the center of Fairhaven as a whole.

Art by Dana Knutson.

...I am getting zero kicked back from search engines on this one. Undying Court gone wrong? Venerated form of undead within the Blood of Vol?

Eberron could never seem to keep a firm decision on gnome vs halfling ears. Raven is a nice reminder for scale.

And here we have our iconic Master Inquisitive, with a wonderful breakdown of their toolkit as well.

Eberron did a great job of leaning in on unexpected roles for different races/heritages.

...but there's always still room for the classics.

This looks like it made it to the final version pretty much intact.

Talenta heritage on display here with the clothing and familiar.

Symbol on the sleeve looks similar to the Sovereign Host.

Too late to be Lidda, too early to be Merisiel.

It is very important to be both powerful and sexy.

...but why the toes out?

Fine upstanding Riedran citizens.

...that's not a horse. Some kind of Quori ?

Looks like her ethnicity, along with vestment styles for Silver Flame worshipers, were still being nailed down at this point.

Washed out, minor style change in naming.

Another set of alternate names. This would most likely be the White Arch Bridge, destroyed (more than once) during the Last War.

4?! We were going to have a Kaius IV?
I'm utterly dismayed we were denied that potential blood-based pun.

Hard to tell from the architecture and armor, but this might have been an early version of Breland's "King's Citadel", or one of the throne rooms in the Five Nations.

As mentioned earlier, we can see some of the intermingling of ethnicity here, compared to the Five Nations, but not so far afield as the Serens.

Hello Erandis.

I just love that little fellow there.
"Stay back, foul creature! Bloodthirsty monster!"
"...dude, I am literally just hanging out."

Got him quite right from the start, it seems.

Later to be known as The Cogs.

Another blank, and I am OUTRAGED. MOLE SHIP?!

...honestly a Monk of the Mockery would find this being left blank intentionally to be hilarious.

War doesn't differentiate.

Carcass Crab early name.

...just come out and say the Mror Holds are the Swiss already.

They disappear if they turn sideways.

Bring your pet to work day at the bank.

I have so many questions. Practically unrecognizable compared to Scorrow or the Mockery-worshipping Driders.

The asymmetry makes this especially creepy, which is probably rather the point.

*sounds of seasoned adventurers screaming and running in terror*

Your average experience with riding lessons on a warmblood.

Probably the Argonnessen one mentioned earlier.

Welcome to the frontier lands.

Another monster I can't find reference to ANYWHERE.

Appeared in Monster Manual III.

Lightning Rail early designs.

Look how tiny the people are next to it.

Lhazaar natives, most likely.

More inconsistency, or maybe just variations in genetics, for Halfling ears.

Assuming these are portable temporary stables for the flying mounts.

This looks much more like the Riedran architecture we saw in print.

I'm just going to guess this lives in Xen'drik somewhere.

Lack of Silver Flame symbols mean this may be from before Thrane and the church were really integrated as effectively one and the same in the lore.

Hey look, it's Argonth.

Someone in design liked ibexes, but thought 'but what if more?' I guess.

This is better 'mundane' horse anatomy than I've seen in most fantasy art.

The Valenar seem to be another group they just got it right in the early waves and kept it.

...that really doesn't narrow it down that much.

"It's my day to carry the flag!"

more like juggerYES

Early name variant, sadly blank.

Oh, there they are.

Well that doesn't narrow it down much.

This is such classic penny dreadful exploration era type composition.

Early name variation, but the style marks seem to be already set.

FINE GNOMISH GOODS! DIRECT FROM TROLANPORT!!