They look like http://images2.wikia.nocookie.net/__cb20071231032638/starwars/images/4/4a/Ewok_village.jpg
No. Wait. Wrong fandom....
According to the 1st PGE, Valenwood's cities aren't actually built by the Bosmer themselves. It never really says if that means they were taken from the ape-race or if they were built by outside contractors. The 3rd PGE edition sort of suggests that the cities
were built by the Bosmer (It says something to the effect that the major cities grew up from trading posts, but that's still pretty vague). I believe the in-game book series http://www.imperial-library.info/content/dance-fire has some stuff about the Bosmer. If you feel like reading.
I'd also be willing to bet that they use more than just your typical animal bones and hides to build stuff. I'd imagine they'd have some pretty big bugs down there; I could see the Bosmer building structures out of carapaces and such. Kind of like how the Redoran buildings of Morrowind are made of giant crab shells.
I'd disagree on that point of not using wood. It doesn't represent a rule avoiding, legalistic approach that the border states would assume for ease of trade. Limiting their use of material without question seems like the odd complaint copout that no culture would actually take seriously when they had a benefit from it. I'm sure they have their Amish equivalents in the province, but I'd bet they'd have a much stronger impulse to bend the rules. Things can't be as simple as this "green pact" would imply.
Edit: And as for rules, they actively let people harvest their trees left and right. There is wild naivety if someone in this forum thinks there aren't Bosmer on the take.
I'd actually have to disagree with the disagreement. I'm sure there are Bosmer who would bend the rules, but that seems like it would be the exception; the "Amish Bosmer" would be the norm. When Y'ffre helped them adapt to Valenwood, they promised not to harm Valenwood's forests. In a reality where the gods are basically real entities, that seems like it would be something they'd take seriously. And I don't think they're not too keen on outsiders harming their forests, either. Or at least not Khajiit. That's pretty much what
Mixed Unit Tactics is all about.