You can improve a lot by just changing the tile set into to a real screen 4 tile set.
Try to count how many tiles you have in the maps: I think that each level fits in 256 tiles
plus some animated one (bosses apart).
Do you have time to make the musics for Turrican Msx? Wolf.
The idea is to make versions of the best Turrican songs between Amiga-Snes and some originals counting that you are a great composer.
For SCC of course.