Hey RHDN, I have yet another question, two of them actually, but I'm gonna get the easier one out of the way first.
I'm not much of a stranger to palette hacking, especially in NES games, but what bugs me is that I can't change the background colors in Super Mario Bros. I know it's possible, and many SMB1 hacks on this site use unique background colors in their levels. While I usually have no problem changing palettes for sprites, foreground objects, etc. in a hex editor, the background colors themselves are a different story. I can try editing the hex value for one of the background colors and more likely than not nothing happens to the background color. It really annoys me because I'm not a big fan of either the very light blue or the flat black.
If I can get a solution for this, that would be very nice.