One thing that immediately pops out to the viewer is just simply how adorable the girl is. You chose to work with a fantastic scan, Kat. Not only does the painted looked really suit her nicely, but it also helps add to the entire atmosphere of the wallpaper itself. I really have to stress how much I really like it. While it would of been nice to see the other two girls in the wallpaper, I can see why you didn't put them in and I think it was a great choice not to as well.
One thing I really liked the most is the background. While it does present a style that has a similarity found in your previous works, it really fits with this character. I actually love the combination of moments too. It sort gives almost the sensation she's famous and a bunch of people are taking her photo, but it also sort of gives a winter-wonderland type of impression. The hearts and stars were a cute touch to it as well. Still, despite however it is viewed, it really gives the whole feeling that it's truly a magical scene and that's what really takes me in with this background.
I have to say this really turned out rather nicely. Overall, everything comes together rather well and makes for an incredibly cute and peaceful background. You really did a great job, Kat! Be proud!