What? An app that lets citizens take a picture of a street art, graffiti, unusual signages, etc and post it on a portal with a mapping interface with comments and their views on the same.

This will create an inventory of sorts of urban/street art and give a place for urban art enthusiasts to share their unique discoveries. This will create a dialogue among the group and may lead to mixer like events, thus enriching the experience of the city.

Can be used as a reference by tourists interested in these sights.
Ofcourse the idea is not to promote vandalising public space but to recognize the unique feature