Well,
I think that it's really cool to document others work. There are many things that photographers photo w/out realizing it was somebody else artwork, e.g., buildings, bridges, sculptures, water fountains, etc. As well, there is something to be critiqued from the photos presented...#1--The crop is off and makes the photo look unbalanced. #2--Once again, a funky crop giving a strange perspective. #3--You've got some keystoning going on. #4--Poor cropping and photo taken w/out regard for the "horizon."
If you wish to continue to shoot street art because you really like it, I suggest you find a way to present it in a new way. For example, use frames (photoshop, paint shop pro, etc.), incorporate real ppl., try and capture the pulse of the community, or give a taste of the bldg--heck, maybe try some HDR. TBH, I suspect many of those street artist would love to see their work in print, i.e., postcards, posters, album covers--the list goes on.
Personally I like the photos, but think they just need some presentation forethought.
have a good one
3Eo