This is a real usecase to support street artists without 3rd parties.
Well this sounds like a modern way of tipping the street artist. And unlike the traditional method, you can do it even after the work is finished. I'm a bit surprised this hasn't catch on earlier, anyone who'd like tips should be adding Bitcoin address qr-codes to their job. You could even use separate addresses to find out which artwork received the most appreciation.
Just make sure to use the lowest transaction fee (1 sat/b), don't worry, the artist won't notice much difference if the transaction takes 1 hour or 1 day, as they are not waiting for it in front of you before moving to the next job...