It seems there is really nothing to do with backgrounds, or at least not too much for now, or maybe I´m doing something wrong, but I´ve been trying hard to improve the train station background (md1stin) and no luck in game. First thing I noticed was that the resizer plugin from photoshop will cause a not matching background with those ugly green lines. Another problem was that after I import back the edited pngs (without resizing them) in Palmer, and after saving and re packing the flevel lgp file, and ofc after I copy the new png files which palmer creates after saving the field file, in the textures folder (in this case 5 png files, from "md1stin_00_00" to "md1stin_04_00"), all I get in game is an error while loading an unexisting png file called "md1stin_04_12", so idk what else I can do to get my edited backgrounds working in game... :-\
Did anyone have any success doing this before?