And these citizen themselves will not take picture because the "picker" ask them to do that, will they? Like, "hey, there are some trash out there, can you take some shoot of it on this condition, while I pick it, and the cleaned ones after I pick them"? Because if that's your concept, then we are going back toy previous question of how will you be sure the trash was not a mere set-up by the cheating picker?

And if your concept is the entirely opposite of the illustration above, you assume that without anyone asked their help to take a photo evidence of trash lying around, the citizen will miraculously have an initiative to do that, then waiting for people to take that, then take another photo of an already cleaned street, the whole scenario will be a little bit twisted, isn't it? Because if they do, then their moral compass need a better calibration. They waited for someone to take the trash instead of cleaning it up themselves. The aim to raise trash awareness is utterly failed on this scenario