Really like how you combined retro motives with the more contemporary cartoon-like style of illustration! You also really nailed the colors! If I had to criticize anything it would be the placement of both the front and the back motives - I would make them a lot smaller on the tee (like 30 - 40% smaller)
This is a really great entry, because the style appeals to most age groups, the color is striking, and you captured the theme very well. The design on the front, between the shapes behind the girl and the colors, almost looks too busy, but the colors are so strong I don't really mind. This is nifty work you've done on this design! Please see mine at [link] and vote if you'd like, thanks!