Thumbnail Beauty

A person, usually female, that is only attractive in a thumbnail image. This is similar to HFFA.

Josh is browsing on the Internet when he sees a thumbnail of a girl.
Josh: Oh, she's hot!
Josh clicks on the image
Josh: Shit, she's a thumbnail beauty!
Josh then proceeds to vomit all over the screen, probably in an attempt to shield his eyes from the girl's ugliness.