Aha ... it's a theme that you want. So how about this:
(edit: new backstory in development)
The SURT virus affects both structural libraries and active processes on the system.
- Some of the 16x16 tiles (data blocks) that are the building bricks of the environment are corrupted (i.e. merged with a tile gathered from a randomly-generated sheeet)
- depict at least two "monitoring bots" (typically multi-sprites) with parts being replaced by some derivative of the generated sheet)
- include at leas two "completely randomized" process, that are made only of SURT sprites derivative
- pick two sprites and turn them into larger (background?) structure.
How to proceed:
- Generate a sheet, select your mandatory tiles (4 blocks, 2+2 sprites and 2 larger structures), post them on the board unmodified.
- Follow the GBA constraints: 555RGB colors, 4 planes + sprites, 15+alpha colors per sprite and per 8x8 tile, 16 tiles palette and 16 sprite palettes at most.
- an entry is a 256x192 mock-up with revised versions of your mandatory tiles. The shape of the tiles must be identifiable and may not have been altered. You're free to colour them as seen fit