I don't know if I would call that either art or trash, but I will say that I have seen walls covered with worse things. Perhaps the distinction lay in the location of those walls.
all in the eyes of the beholder...if I squint my eyes, to add more distance, the colors and texture's blend into a fascinating collage...for me...this transforms the image to art.
It looks like a collage surely, but hope these are not the walls of heritage buildings.
Your photo is art...the walls themselves, trash. I can feel the dirt and grit of the city and I want to just clean it up!