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, GBMB, GBDK, Zal0-ZGB)
Tilemap Helper : A GIMP plugin to help with creating tile maps and tile sets for games
Allows files created by Harry Mulder's Game Boy Map Builder and Game Boy Tile Designer to be converted in to different file formats for use in Game Boy game development (e.g.: with GBDK)