I think the main aim of it not being in the photography gallery falls within the same argument as copyright - it simply isnt your art... I'd go one step further and say that your photo posted above is not your art even with the frame and bit of floor.  you are effectively showcasing someone elses art and not creating any yourself...  That should be the deciding factor in whether it should be allowed in the photography gallery at all.  I also think this would allow for those who take photos of their own art to showcase here in the 2d gallery... easy distinction (and hence why it was mentioned earlier that it is on a case by case basis...)

Now - say you put someone else into the frame interacting with the art on the wall, now that would be ok, in my view, as you are taking somone elses art and interacting with it, thus creating your own...

Incidentally is that monk giving us the two finger salute?! 

"In every colour, there's the light.
In every stone sleeps a crystal.
Remember the Shaman, when he used to say:
Man is the dream of the Dolphin"

Rich Meadows Photography