Here is a hack for Batman which changes most of the enemy sprites in the game. Also the playable character sprites have been changed as well as some of the level graphics.
Batman - The Video Game (USA).nes - NOINTRO
CRC32: 395569EC
MD5: 2E9F52556273AA735D0E75649541D812
SHA-1: 73B33E67E3C9E1116F9FCB021B10BB1171B8696A
SHA-256: B309BA13D978CE2CC12BC0878886CC1560B8EACBFF55015E56AA7F3609F8CFEC