OBGBTC

OBGBTC (Onboard Gameboy Tile Creator) is a tile designer application for the Game Boy.

User guide

Back the Ram bank the Tile data is saved in (with Bung carts use the "-bsn switch").
Open GBTD.
Set your TileCount to 255.
In the File Menu select Import From...
Either type in the name of or browse to the File created in step 1.
In the import dialog, set the type to Binary 8x8 Tiles.
Set the Tile Count to the amount you set in step 3.
Set the Format to Gameboy VRAM.
CLICK OK your tiles should now be the tileset you edited on the Game Boy.

On the File Menu, Click on Export To...
Set the type to All-purpose Binary File (*.bin).
Type in the filename you want.
In the To Block Type in the last number of the tile you want to export.
Click OK to create the Export file.
Use PadBin.exe (Available elsewhere on this site) to make the file 8KB for the ram bank.
Write the SRam File to the Cartridge (with Bung carts, use the -lsn switch").
Continue to edit your tileset wherever you want (on the Game Boy).