I personally don't like these games, but what image format do you need these images in? If it's AGA at the moment, I can't help you I'm afraid. However I could design them in HAM mode and send them to you on disk for conversion. If that's possible.
These sorts of backgrounds are generally built in chucks on an axis aren't they, how big do you require the chunks to be pixel wise?
:-o PM me with details, I'm interested! :-o