Some images seem overly compressed and look pixelated. Where we've seen this most often is on background images and images that use parallax. They look grainy and pixelated, which gives it a low-quality appearance. On images using parallax, it would be nice to have a little more control over how it looks. Sometimes it appears like the image is zoomed in, which doesn't look good.
Possibly there could be more settings for image compression and how images with parallax appear.