[NHervé]

Well, all VRAM handling should be rewritten...
In NSMB, the mini-games have bad sprites due to faulty VRAM handling...
I found how do they work :
They map the bank D as BOBJ and I as <Disabled> and write the sprite data in BOBJ, then they map bank D as LCD and bank I as BOBJ, and write in BOBJ some data for the pause buttons, and finally map bank D as BOBJ and I as LCD. When I press A (pause), the bank D gets mapped as LCD and the bank I as BOBJ.

So I can say that the sprite data must be at 0x06860000 (LCD+0x60000, bank D) and button data must be at 0x068A0000 (LCD+0xA0000, bank I).