The angle of the reflections is somewhat odd. Just looks like it's been flipped. Reflections are among one of the hardest things for me to get right, so I know how you feel.
http://yfrog.com/0nperspectiveboxj
The link is to a perspective box I made to help me get them right. It might help to understand reflections and shadows a little better. It isn't perfect, but it's accurate enough to work with lol
Don't forget that there would be a shadow under her if the spotlight is directly overhead. There would also be shadows on her because of her lips, hair, nose, etc.
A plain background could work well with this if you got rid of the logo or shrank it down and put it in a corner. The way that the logo is now makes it a second focal point and takes attention away from the little sister. Sometimes going simple is better.
The little sister herself was very well done. Great job with that, especially the dirt/blood. I also like the spotlight because spotlights generally add a dramatic feel to the subject.
Don't get discouraged if you make mistakes. It's all part of the learning process. One of the reasons why we're all members of the Void is to learn from one another. Keep working and you'll see improvement. Rome wasn't built in a day.