I changed something somewhere that changed the dungeon background to green instead of black (like the entering and exit routines and the holes) does anyone know what could have cause this? I usually write down all the changes i make, but for some reason i didn't write this one down, and I seem to have forgotten what i changed.

Don't know how helpful it would be, but a file comparison might help to narrow it down a bit.
If using Windows, use the command prompt fc /b file1.smc file2.smc >result.txt