I couldn't find this issue anywhere on the forums (if there is a thread to this problem, please post a link).
Thanks to a user I was made aware of the fact that ALL of my HD wallpapers with a resolution of 1366*768 have a 1 pixel large white dot in the upper left hand corner of the image. As far as I can tell none of the other HD resolutions are affected. Since all of the HD wallpapers I upload are in 1920x1080 I can exclude human failure as a possible error source.
Does anybody know how I can prevent this from happening? Perhaps in the site settings? It would be a real pain in the ass if I had to create them manually.
Thanks in advance.