While it really helps give a sense of volume and looks good generally speaking, I wonder if it should be done in this case, because roguelikes are mostly indoor dungeons with small sources of light. . . .
Well, that's the thing...right now, I'm not seeing any light sources (torches, etc), and the room overall looks very bright. The tiles would probably look really cool if you made everything really dark and moody and added torches or whatever to all the walls, with shadows all over the bricks and stuff, but that'd be much harder than what you're doing right now (I know I couldn't handle it - I'm trying right now!)
Without any light sources showing, I think you should use the shadows r1k did. Besides looking less plain, they also help the walls look like they're more attached to the floor. Also, I think those sorts of ground shadows will help with readability a lot, especially in tight corridor areas - the blue tileset you keep showing, with the bookcases and such everywhere for example, I have no idea what's going on on the bottom of those pictures. I can't tell where the walls end/start, or whether they're supposed to be higher than the other walls. The whole thing looks like an optical illusion, hahah! It actually reminded me of one of those impossible "how many legs does this elephant have?" pictures. It's because without shadows on the floor, your blue walls very easily read as holes instead of walls (at least to me). Your red stone walls don't suffer from the same problem, because the texture of the walls make it obvious that the stones are overlapping, where the flat blue bricks don't do that.
Anyway, pretty cool tileset. It's very easy on the eyes, and looks interesting enough. =)