Great vibrant colors --- I think this shot had oh so much more potential than you allowed it.
You shot pretty much straight on and the image is fairly flat, a different angle would give greater depth of field.
(Are you opposed to laying on the ground and shooting up?)
Focusing on one dramatic part of the wall and letting the rest of the graffiti frame your center point would give it more impact.
Love the graffiti colors and artwork- I tried to find something like this in my city but I guess we just don't have the good street artists here! I think this shot would have looked better with more depth, more of the parking lot in the foreground. (maybe that wasn't possible)
The concept is good, but the composition somehow leaves me wanting. There's so little foreground and sky that they seem like distractions to the photo. Yet, I think it would be a weaker photo with only the graffiti. Perhaps if we saw more of the parking lot...?