Hi! Great Tutorial! Its a very useful Thing!
Now, the Hardware supports (16*16) *2 In Total, But, For Minisprites use one Part (16*16) and it have some Palets of Tiles Too.
For Better Understand of Wath i means, Open Any .gba Rom with VBA and Go to "Tools > Pallete Viewer" The Right Part Its Used By Ow's
Sorry for My English x'D
Have a Nice Day