Well, technically, all of the 2D images are actually 3D models, so yes, I suppose it's possible, but very hard and would probably surpass file size limit.
Hmm. A cylinder may be hard to find. The best I've found is the franklin badge, which has a fairly large texture for something so small (128 pixels square), but the side doesn't texture well.
As for a semi-circle, I wouldn't know where to find it.
.OBJ importing would be ideal, of course, but it fails a lot >.>