After enabling dark theme for the website, I noticed something on my game thumbnail:
There were two white strips in the thumbnail. This is due to the thumbnail being a bit wider than the recommended size, so the image was fit into the space. In the light theme, this is unnoticeable; however, seeing this in the dark theme makes the thumbnail look like it was poorly cropped.
If the white is from the background of the page, it would probably be a quick change. Sorry if I’m being demanding, but it creates a sense of un-professionality for the game.
In conclusion, It would likely look much better as black stripes.