Can I upload a photo that I have taken of another photo, painting, sketch or picture?

If you are the author of the artwork featured in your photography then yes, as you have the image rights.

If this is not the case, it is an infringement of the intellectual property law and your photo will not be accepted.

If there is artwork (i.e graffiti/street art) appearing in the background of your photo but is not the main subject, your photo will be accepted.