I think that the perfect solution would be using this background pattern:
But I wouldn't mind using a bright background too, it will be consistent with how Kagi handles this type of image before you click in any specific image (like the first image in this thread, where transparent=white even in dark themes).
Edit: actually, thinking again, it would be very cool if Kagi creates it's own transparent background pattern, it's very confusing to see if the image has an actual transparent background or is a real white-grey chess pattern in the image. Something with the Kagi dog mascot would be very nice 🙂
