Well given that the engine itself bears "RPG" in the name, it sorta gives you more or less of an idea of what you can and cannot do,
RPGs? that's a fact, Active Battle systems similar to those of Zelda or Seiken Densetsu, with the right scripts, indeed possible,
platformers? I've seen some in VX, card-games? haven't seen one.
racing games? that's a tough one... afaik it MIGHT be possible, but don't expect it to run or appear as smooth as another racing game
ok now...
using an image as a tileset? of course, all you need to do is change it's size so it fits into the tileset template then upload it into the
tilesets folder. although you might have trouble when giving properties to such a tileset.
if the image does not fit (too large or small) what I usually do is export one of the default images that RPG-MAKER comes with
(tileset, character, animation, whatever you need) and then paste the image on top so I can use the borders as a way to find the right
size, once that's done I just import it to the folder I need.
just take note that sometimes resizing something might make it appear distorted, so use it as you see fit.