At most, you would get a Cease and Desist order from Nintendo if you released the game to the public (rare if is a free game and the better/popular the game is, the bigger risk), but probably not a good idea to post it (the game itself) here because the staff will report you.
Just look at what happened to this guy -
http://www.pokecommunity.com/showthread.php?t=305337
Cool people like ZUN (confirmed) allow fan games and he actually loves it. Capcom also don't care (unconfirmed) if people use their sprites. You know Nintendo though, very strict!