A demo for https://github.com/evanbowman/BPCore-Engine
The engine from Blind Jump cannot display fullscreen images in a single tile layer. But you can display fullscreen images with two layers. I could give more memory to one of the engine's tile layers, so that it can access more VRAM tiles at once, but then I'd need to take memory away from a different layer. Ultimately, the GBA has limited memory, and it's hard to anticipate what everyone will need from the engine.
Maybe someday I'll consider adding a new graphics mode, specifically for fullscreen images...