Probably the wrong place to post this but I'm not sure where the right place would be. lol

I never seem to be able to make a satisfactory thumbnail for my renders. They usually end up a little grainy at the very best while staying below the tiny 15kb maximum, yet I keep seeing beautiful thumbnails from others in the gallery. I prefer to create a cropped thumb over the site generated full view. The only tutorial I've found so far was for 100 x 100 sized images which is much smaller than I would go with.

If anyone has any tips or a tutorial link it would be greatly appreciated. Thanks.