I see the point with the rotation stuff. I think maybe a good test would be to take a Boktai floor tile and rotate it, see if it would work for a topdown game?
How does your program compare to the RotSprite one? that one was pretty decent
Pistachio I'm almost sure someone in here posted something like that. Cant remember right now...
Oh, also for non-pixel stuff AlienSkin BlowUp is great...maybe you can take some ideas from there?
Also, when thinking of rescaling I feel the need to mention this
http://www.youtube.com/watch?v=vIFCV2spKtg&feature=player_embedded for no particular reason...just that it works very well, maybe some of that logic is necesary when downscaling?
Other than rescaling, there's a filter I've always really wanted to put my pixels trough, it's that TV look filter, Like one of those NTSC filters you have in Kega and Zsnes emulators, if you can do that it'd be great. I asked the guy who makes those filters and he gave me some libraries, if u want em I can send em to ya :p