Well, it's not bad, but it's not really that impressive. The thing about those iPod-type things is that they are too simple. I've never used photoshop, but I know that if I got the program I could paint a monochrome background and stick in a silhouette in about ten seconds. Is that really your BEST one, or is it just your favorite?
You should improve on making the headphones look better. Right now it looks like you simply used the pencil tool and just drew the headphones one, making the lines not smooth and huge headphones, comparatively with the head of the person. Also try to put more things in the picture or make the people a lot bigger because the emptiness makes the picture unappealing.
Not sure how you made the silhouettes are these are many many ways to achieve that in PS but from the looks it's as if you marqueed it and filled it with black making the silhouette way too smooth and blotchy with undefined shapes. Also why does the second person from right all of a sudden have a shadow between the legs whereas the other characters don't?
Anyway, just my suggestions on making it look better.