Very nice! I like that you did NOT make her undies white, because that could be perceived as her wearing a swimsuit-type jumper with a skirt around it. Of course, making the undies the same color as the skirt gives the impression it's a skort (shorts built into the skirt).
My suggestion? Make them pink so they stand out as lingerie and, therefore, a little bit sexier to get a peek! :) Yes, I do think about this stuff when creating my own images.