After some debug, I've some questions:
1.- How do I have to use Loopy's palette (as it has 64 entries while a real NES only has 32)?. I mean, which entries do I have to use for BG and which for SP?
2.- I've realised my emu's showing incorrect colors cause I'm not handling palette writes. Then a problem comes to mind: how do I change the color values of my external palette? I'm using Loopy's one, so when a palette write occurs, how do I change its values?
3.- How does 'Super Mario Bros' write to Name Tables? Actually, it isn't writing anything on my Name Tables, so when I run it, it only shows '0' tiles. (???)