I guess its OK if its still triple licensed after being worked on, so the next guy that works on it still can pick his license. Not that I'm going to work on the graphics... my graphic skills is practically non-existing unless you compare to my music talent. Just a thought.
That's up to the artist. Personally, I'd just pick a license and stick with it, makes things easier.
I guess only GPLv3 and never would be a problem too... or are the project moving to it?
There hasn't been any serious discussion about it. I'd like to move to v3 without any added restrictions as it clarifies a lot of things that v2 leaves ambiguous, but I'm not the only copyright holder here and having several licenses within the content isn't the greatest of ideas.