tgbedit
I spent several hours throwing together a tile editor for the Gameboy since I couldn't find one that would work on my Raspberry Pi. I didn't want anything too complex, since it's just something I wanted to throw together so that I could start writing up little tests.
Upon completing those several hours labor, I pulled up the documentation for my assembler, and found out the assembler package came with a utility to convert PNG files to Gameboy binary files
:/
BUT...
Now YOU TOO can uncover the indescribable horror that is the WORST GRAPHICS EDITOR OF ALL TIME!! Compatible with Gameboy and NES tile formats! Marvel at the sheer audacity of attempting to write a graphics editor WITHOUT USING A GRAPHICS LIBRARY, OR EVEN CURSES, OR WITH ANY MOUSE SUPPORT
How on Earth could one write a graphics editor like that? CLONE IT AND FIND OUT!!!
It's compatible with anything that can run a Python command line! So there's that.