It would be nice to have the option to change the background behind the image preview with a light/dark option. It's no biggie with JPEGs, but the transparency of the PNGs when part of the image is almost the same color as the background renders the preview almost useless for quick viewing.
Notice the difference below between the dark version of some icons vs. the light versions.
If not having the option to change it, perhaps a global fix would be to make the background you already have a more neutral gray?
Thanks for considering this!