Very nice
This is the first image on Newgrounds I've seen that got screwed by the way it displays images, but I suppose there's no way you could have known that. When you fullscreen the image to get a good look at it you can't see much because the black of the image blurs with the black of the preview :( The small one wasn't good enough to review either so I had to save it and open it up in Fireworks and give it a white canvas...no big deal though took all of about 5 seconds.
The art itself is good. All the art in the image blends together very well into an urban looking, paint splatter styled image. Lots of cool stuff going on here I see a lightpost, some flower looking things, something that looks like a leaf, love the circles - I'm a whore for putting those in my images too.
You chose a graffiti style font which I think was very suitable and the color seems to fit the image very well. I suppose the slightly off colored paint splatter filler was a good call as well so it doesn't look so boring.
As far as criticism goes, I think if you have any more of these transparent images you should stick them on a white background if they look anything like this one so we can see the image at full resolution. I suppose as far as the art itself it really feels like the area around the building is kinda the climax area of it and I suppose you could have expanded elsewhere to give the picture a real full feeling. Yes, it already has a pretty full feeling but it's a good piece of art so I'm reaching here for criticism :P Keep up the good work.