Figured out how to convert the title screen into tileset format the game needs, only problem is I got no idea how the game actually matches up tiles against it.
eg. here's the tilemap in pret:
https://github.com/pret/pokeyellow/blob/master/engine/bank3d.asm#L290I don't get how it could be using tiles $80, $81, $82 (128/129/130) etc, when the tileset only has 107 tiles. I guess it's maybe indexing into VRAM tiles or something, but idk how I could figure that out.
(before anyone mentions it, I know the pokemon logo shouldn't be part of the same set as clefairy, I can change that once I figure this crap out)