By internals here I mean still outside, just not on a world map, but outside of the tower... unless the player goes inside the tower straight away, without coming up close to it (but even then, I didn't notice any specifically tower's insides)... I've just been encountering these problems since I started actually, e.g. the yurts too on the snow fortress map... no internal yurts.
You can make a yurt\tent interior by using the cloth looking wall tile. It doesn't look very good in my opinion, though. Some of the resource packs come with tent interiors that are all pretty and nicely shaped, but the default stuff has nothing like that, unfortunately.
Yep, there are tent objects, but not tent shaped interiors; gotta put up with that blocky goodness. The sci-fi and modern sample maps are way better than the fantasy ones, in my opinion. Whoever made those looked like they had a lot of fun.
I think I finally get what you're talking about. You can actually find some of that stuff in the resource forums made by the community. The RTP always leaves some holes, so yes not every "buidling" in the world map tleset has a corresponding one on the outside tileset.
Frustrated, as always. I took a break from working on games and when I turned back to working on them again, bam! Slapped in the face with more errors. Such is the pain of working on any project, I suppose.