I know I'll sound like a contrarian, but if OP wants to make a 16-bit console hack, then he should just start on that 16-bit console.
When I first started seriously ROM hacking, I wanted to start on the PSX. Everyone told me not to, but I did anyway. I wound up learning about PSX textures, CLUTs, ".TIM" files, etc. without having to learn extraneous details of NES graphics that I never needed to learn anyway.
OP, just get straight to the game you want to hack. Beginning somewhere else and then moving to the console you want to work on will just be confusing since you will have preconceived notions of one console that aren't applicable to the other.
I imagine that if I did start on the NES and tried to apply what I learned there to changing the textures in a PSX game, it would be confusing as Hell (as opposed to just start learning on the PSX instead).