There are lots of bricks pattern out there. Search on imageafter.com for example - cause now it looks a bit fake.
Also give depht to the window, so that it won t look like paper.
Here's an awesome tutorial about making a stone wall - use it to make your bricks real, before time runs out. http://www.lunacore.com/photoshop/tutorials/tut028.htm
Best of luck!

Nice idea, but the bars are to far from each other, so this little fella can go out when ever he want...

nice idea but i think that instead of red bricks it should have been white blocks... like real jails becuase the red bricks to me kind of represent stereotypical school house!! haha but the idea is great . good job