I wanted to inform the SuperTux Players that many old Backgrounds are going to be removed, as you can see here: https://github.com/SuperTux/supertux/issues/1143
If someone is against this or even uses some of these in his levels, he can let me know here. But my first suggestion would be to use the newer, better backgrounds, which have been contributed by BlasterMaster and others.
Regards,
Serano