Thinking of making a NSMB hack

Just so you many of the NSMB "sprites" (characters, enemies, obstacles) were actually 3d models always viewed side on so they appeared as 2d. You will need to play 3d hacker to get at them- http://kiwi.ds.googlepages.com/nsbmd.html has some http://www.romhacking.net/forum/index.php/topic,8407.html has more.

Most NSMB tools I see are straight up level editors- you make a bunch of building blocks for various things and then put a bunch of them in there to make a level.

The backgrounds on the other hand might well be 2d but background hacking is ever so slightly different to sprite hacking in that there are probably no simple "how to make" type files like there are for sprites. The setting the bit depth, choosing a palette (or not for bitmaps) and shifting start/pixel header type data is the same as regular tile editing.

You could spin this I guess and attack the video memory itself but how that works for 3d and if you want true monochrome (a small number of colours sure but proper monochrome/greyscale........ maybe as an emulator hack like the his res retexture stuff on the n64)