It was discussed a bit when Ulduar came out: There could be a multitude of explanations, the first being they mean nothing.

However, the name "descent into madness" is the Old-Gods wing. We know (now) that it was also Old-Gods that offered Azshara and her followers immortality (via Naga transformation) to live through the Sundering. It wouldn't be too much of a stretch to conclude that the Titans were artistically displaying the Naga, as a means of representing the Descent into Madness other races have already devolved into - as a result of Old God influence and corruption.

I'm not sure if the timelines for this work out. Were the Titans still around/did they build Ulduar after the Sundering? If they knew about the Naga corruption via another Old-God, why would they just leave Azeroth?

I want to believe the glass windows really mean something more and have a solid reason for being there, but I think it's more likely it's just a little easter egg Blizzard gave us (a slight nod to the Old Gods and Naga connection: which is yet to be fleshed out until another expansion)

I honestly think the stained glass and holograms just mean nothing lore wise and are just there since they look 'cool' and most likely do hint towards the future. We don't know exactly when Ulduar was built but I'd imagine it was built pre sundering considering the Path of the Titans seems to have been pretty destroyed during the Sundering and leads out into the ocean.

Aye, good point. Who's to say that the reason it took them so long to release the new forms isn't exactly because they've been working on art for 4 races and the design team just recently decided what the other two races would be? But hey... I'm just playing the devil's advocate here :P

Well, there are the constellation artworks in HoS and HoL that also meant nothing until we saw Algalon's model. Maybe not playable races, but certainly something that existed in the Titans' calculations when they built the place. Maybe a prophecy of some sort, or omens of how to tell if Azeroth was corrupted. Still, fighting the naga would be a good way to follow Algalon's lead to save our world :P

I really doubt the constellations mean anything since a few of them are of races that didn't evolve till after the Titans finally left. Sure we can play along that the Vrykul were created based on Algalon though. The Titans didn't know anything about the Curse of Flesh or effects it would have until their second return and the Vrykul didn't start having mutant (human) babies until after the Titans left. The Titans thought they fixed the problem with the Old Gods so I really doubt they were thinking that humans and other such races would ever come to be since otherwise Algalon wouldn't of been ready to tell the Titans to destroy the planet. We don't know when Ulduar was built but it was most likely pre sundering and probably before a tribe of trolls turned into night elves and Blizzard failed to actually give us taunka lore and whether both tauren and taunka were around or if one evolved from the other (and as far as we know the taunka/tauren are a natural evolved race on Azeroth).

I think much of Ulduars decorations have no true lore tied to them and were merely done to give it a Titan like look.

Actually there are Dwarven druids among the Wildhammer Clan.

Wildhammer clan - WoWWiki - Your guide to the World of Warcraft

Don't forget there are Blood Elf druid npcs as well. I am guessing Blizzard didn't create Blood Elf druids as being playable since they didn't want to spend development time on new forms and Spacegoats obviously not being druidic.

http://images4.wikia.nocookie.net/wo...t-Freywinn.jpg

Freywinn is the only blood elf druid, either in game or from outside lore. I consider him an exception, rather than an example of a broader truth.

Wildhammer druids only appear in the Warcraft RPG. That source also allows for human druids. I've never seen any, but I started playing WoW just after the honor system change, late in vanilla. That would explain their inclusion in the sprite darter hatchling quest chain; I wondered about that.

If Blizzard went the route of just adding current classes to the current races then blood elf druids seem pretty feasible to me.

Blood Elf Warriors before Druids I'd think actually. They're literally the only class/race combo held back due to game mechanics(Blizzard had to limit themselves to 6 classes for them).

Since we're talking about possible Druid-able races, lets throw in Shaman and Paladins also, since I would expect Blizzard to add those classes available to another race per faction for the same reason Druids would be.

Pandaren - Works perfectly for both Druids and Shamans. Possibly Paladins too, but that would be stretching a bit.

Goblins - Shamans for sure. Druids and Paladins probably wouldnt work too well.

Worgen - Druids and Shamans would work easily. Paladins not so much.

Bipedal Naga - This would be a rogue good aligned Naga faction. Pretty much all three would work easily if they wanted.

Satyrs - Shamans and Druids would work pretty easily. Assuming they are an Anti-Xavius good aligned rogue faction. Say what you will about these guys as a playable race, but they thematically fit better than any other race option minus Naga for a Maelstrom/Great Sundering themed expansion.

Furbolgs - Shamans and Druids easily.

Drakenoids/Skardyn - These are more or less a clean state and could easily be fit to use all three.

It's literally been said by Blizzard had to drop one class from Blood Elves for mechanical reasons at the time. They had to choose between Hunters, Rogues and Warriors as being dropped (They wanted to keep all three pure casters and Paladins obviously), and decided that of those three, Warriors were the least best fit. Warriors were originally planned in vanilla to always be available to all races, hence Gnomes having Warriors, despite the fact that Warriors really aren't the first thing that comes to mind when you think of Gnomes either.