if you have a tin line on top or side of your picture it's because the tile is not a square size 512x512 for example or 64x64 etc that happens quen people use custom size for tiles in the properties of your picture check if its a 64x64, 128x128 etc in px and not for example 128x64px (thats a wrong size) this is solved only by changing the size to a 128x128 etc size "square"