The three components of a GBA background is the palette, the tiles and the map. The tool i made lets you specify the colour in the palette, then draw on an 8x8 tile, and then assemble the tiles into a background.
I added in an export button which dumps the palette, tiles and map in the correct format as a set of Zig arrays that can be copied directly into the GBA memory. In theory this should let me assemble background screens faster (Ignoring the one month I was working on the editor as a sunk cost). I also can use it to draw objects to use as sprites, which will save me some time.
So now onto making a game, I have less than a month to do so before the game jam ends. Luckily I have a reasonably simple idea that should be achievable. Before then I think I should probably add in a load/save function to my editor though, to avoid future frustrations.