What is public art in legal terms? What am I allowed to photograph and submit?
The Copyright, Designs and Patents act 1988 defines Public Art as sculptures, buildings, models for buildings and "works of artistic craftsmanship" which are permanently situated in a public place or in premises open to the public.
This means you cannot walk into a gallery, for example, even a public gallery, and photograph a painting to send to Big Art Mob. Likewise you cannot go to a privately owned place, say a stately home, and photograph and send pictures of art there without permission.