This is a screenshot from my computer, as you can see I tried to blow it up as much as I could at the highest quality I could. Then I did a reverse image search and found nothing. Now I'm really curious too.
The truth is, this could be included for no reason in regards to audiences as a whole. Maybe Tarantino saw it in the location he was shooting at and liked it so much he didn't have it removed.
Maybe it is symbolic though. That looks like the face of a tiger at the top, maybe? It wouldn't explain what's protruding from it's face. Also at the bottom that is probably a flower? I don't know.
There is no mention of this being symbolic in any interview about Kill Bill I found, and I can't seem to find any discussion about it anywhere else either. I'm sorry I can't help you, but I have a feeling that this will never be decoded unless someone knows EXACTLY what that is and brings it up online (such as, the artist of the painting. Is it even a painting?)
Just checked the script. No mention there either.