Talk:Circuit des 24 Heures/@comment-71.190.138.147-20160312162631/@comment-26249703-20160328113103

Actually, it's to do with the file type of the picture. .PNG files can include areas without data (transparent) which is represented by the small grey squares in the preview, or completely white when clicking on the image.

On this site, since the background is grey, the transparent nature of the image shows grey, as opposed to white on the other site. If the image was converted in .JPG, for example, the transparency would be converted to white. Then it's just a matter of opinion as to which is better.