Option Images Scale Up To 50Px Then Down To 20Px

I have a LOT of color options (about 60) so I have my product pages have the image for each preview color show a small 20x20px image below the pull down menu for all of our colors. But I notice that even when I upload the image to CS at 20px it makes it 50 px so I have it scaled back down in CSS to be 20px. Is there a way to keep the image size I upload or have CS where it defaults the option image to 20px? Seems like all the extra pixels being forced to download would be hard on system resources not to mention could cause some issues with SEO.

See attached.

option image size.jpg