I really like the theme and idea if this banner. The window in the middle looks really nice and I love the coloring. The text is a little hard to read, so you might want to make it stand out a bit more. My only other thing is the pictures of Hermione and Draco. The placement is them is very nice, but they're a little hard to see. You might want to brighten them a bit.
Here's my banner. I've only done graphics for a week or two, so any critism would be welcome.