Here's a philosophical question for you.
A lot of people tell us that entering a photograph of someone else's art is not a legitimate competition entry, BUT ......
Where do we draw the line, and indeed is there a line?
Is there a percentage of that image which must be your own work? Or is the way in which you capture it in fact your own work?
If the art is only a part of the image, then how greater a part must it be before it crosses that line? What is the difference between photographing an artistic building or an art work? Is there a difference?
Is photographing graffiti photographing someone else's art? How about if it is in an alley way and is central but not the exclusive focus?
I find that an interesting grey area (possibly because I have one winning image which is 100% someone else's art, re-composed in my own photo).
There are legal aspects here, but also the whole idea of where the border lies between recording or re-imaging art.