Hey, stuh, you forgot to mention that it's a pretty impressive background for the first try!
- What is that crazy colored board on the left wall?
- The whole room looks rather small for a classroom, but thay may have been your intention. (if not, resize the door and windows / make them smaller )
- What is that white thing on the lower right? A power outlet? Not sure about this one.
- Remove the yellow part and vanishing point on top!