Change Image thumb background : How to see white image in thumb?
I don't know of a way to fix this in the Finder. 

The images your are looking at are most likely "web ready" meaning that they have been stripped of much meta data that takes up extra bytes which would slow the loading of the images into a browser. Without a pre-generated icon the Finder creates them on the fly and does not always create a meaningful icon. 

The approach that I take is to use GraphicConverter's built in image browser which is highly configurable and -- if desired -- provides a huge amount of additional information.