ok, i'm not sure if this has been discussed at all, but i dont think it has. i have often wondered if there would be a way to be rid of the portrait of
Sirius's mother. now we know for a fact that it can't be taken down, just like the Black family tree. now i want to know if anyone has ideas on how Grimmauld Place could be rid of that darn portrait. i have a few ideas:
1) BURN IT! (for all u pyros out there

)
Sirius's mother was able to burn a number of names off the family tree, so why couldnt you burn her for the witch she is? (hehehe....) freeze the other portraits in the house so she can't escape from her portrait and burn the portrait and be ready to cast the Aguamenti charm.
2) Tear down the wall entirely and then replace the wall. easiest thing to do: replace the wall. i think i would be able to stand having a missing wall for a while if it meant being rid of that wretched portrait.
i have a couple other ideas, but lets hear yours first.