Theres also some other small bug with some images, also happens when the image has transparency. Happen for example on Era, at the "North Gas Station". The windows are kinda bugged and look pretty weird when you move, but when they are on the top of you Graal window (so when you walk down a bit until they almost disappear) they look ok.
Edit: Here are two screenshots of the problem.
Edit2: And a video ;P
bug.zip