Harry Mulder's Gameboy Development: Gameboy Map Builder
Frame: A map editor for Pokémon GBA games
GitHub - bbbbbr/gimp-tilemap-gb: Tilemap GB - Console App - AND - GIMP plugin for importing & exporting Game Boy game tilemaps and tilesets (as bitmap images or .GBM/.GBR files. Related tools: GBTD,
Gameboy Development Forum / Tilemap Studio 4.0.1: a tilemap editor+creator for Nintendo handhelds