Look good, but all I seem to see is a nice frozen shot of the trick being made. Would work good with a sequence, but try using angles to get somethign that stands out. Get close, get wide, or use your background to compliment them.
There is something about the second picture and the buildign and stop sign. I can't put my foot on it, but I think it has potential.
Edit: Do you have post processing software? Increase your saturation and sharpening. Try burning the shadows and raising the dark levels. That should help them pop a bit. Also adding a simple boarder helps seperate the picture from the frame.
Would you happen to have a flash? If you do, skateboarding is a great sport where remote flashes can really make the pictures stand out, even in daylight.