How would you explain when a persons eyes becomes bigger because of surprise or curiosity? Or when someone smile because because something bad has happened in the past but don´t want to show it. A crooked smile, so to speak.
Curiosity: You could use a comic book exaggeration: "His eyes glitter at the odd sight." Surprise: Again it is an exaggeration, but what about 'bulged'? Crooked Smile: Simply 'lopsided' with context, or else any word that connotes a pull - twitch, jerk, etc...
I like exaggeration too. But why not also check yourself in the mirror? Widen your eyes and see what description pops into your head? Or do a Google image search. See what you can come up with when you have a visual example.
Here is a site that helps a lot. http://www.macmillandictionary.com/us/thesaurus-category/british/words-used-to-describe-facial-expressions Good luck.
