Hello!
Actually, no you are not noob, because I also thought it was some sort of bug, but I figured out you should use square images (16x16, 32x32, 64x64, 128x128, 256x256, 512x512, etc...)
So if you want to use an image for your tiledBG I recommend using a 256x256 image.
Plz ask if you have any further question I am here to help :)