Well about 2 weeks ago i started messing around with smb3 and found some intresting things. There appears to be more unused sprites in the game then most people thought, im not sure if someone has found these already but I havent seen any websites mention them so ill put them here for now.
Well anyways I found some unused Mario overworld sprites.
It seems like Nintendo was originaly going to have it so that mario could walk in all derictions instead of just facing the screen all the time.
and here are some beta buildings I found. (palletes could be wrong)
the first one looks like some kind of wooden toy block fortress thing, the second im not sure what it is and the last one looks like a factory to me, or it could be a beta fortress, the thing underneath the 3rd building is it crushed after you beat the level.
I also found something small but intresting. (palletes are also wrong)
its the mario that appears in mini games, but there are 2 bodys found in the game, one is fatter then the other, the fat body is used in the game but the skinny one isn't, I think originaly Nintendo was going to make a diffrent sprite for luigi but never did, not sure.
Thats all I have found so far, if I find anything else ill put it up on here.