The simple answers for you:

* the reviewpanel graphics can be anything, so long as its a picture in valid BIF format and 68x50 pixels,
* the strategy map castles are BIF or BUF images in textures/campmap/pieces/buildings, and there are 5 or 6 "slots" available, depending on whether you're based around VI - in which case you can provide: stockade, fortified village, fort, keep, castle, citadel (and in vanilla possibly fort --> fortress?). The piece will change with castle level, but not the lesser upgrades. So long as you use the right filenames for the pieces, you could make them look like anything you like - if you want a pink fairy castle with a ring of rabbits around the moat, you could do it