Listen to Saywells!
also, think more about your typography, or to skip the whole "typography" for now, think about your choice of fonts. Especially on the skate-poster. The second image, I have no idea what is, so I won't comment on it. But on the first, you have: a kind of childish freefont, and either myriad or something very similar. Myriad is Apple's main font, and if you've seen apples product-designs then it's quite the opposite of skate-culture. Try some rougher, grungier, streetish fonts.
More comments to come, I'm off
And oh, I think Gino has a blog-entry about good grafitti-style typefaces!