Contra doesn't work: the game starts up but then goes into a death-loop and game over. I tried changing some of the unsure bytes, but same behaviour either way. I'm certain there are still bugs in the MCU core too.

Rik: I got some hints from kevtris. The basic is, you separate the 3 colors, make 3 pictures from the 1 photo with image processing and lots of manual work. It takes about an hour or so. Then potrace(bmp to svg commandline tool).

Zaxxon is possible to simulate the layers, it will just look a bit ugly. Sarayan's svg2lay tool assumes a black background so elements will have a black border around them.