Assuming your fictional world has more than one species living on it, what does each major grouping see as beautiful and ugly? What are the major differences here? The things they have in common? And what happens to those poor souls who are considered to be outside the norm? How are they treated? Can someone be too beautiful/ugly or conversely not beautiful/ugly enough to please their societies?
Incidentally old sayings can be a great source of inspiration for stories from giving you ideas for titles to being the themes for your tales. As for the beast, there's the obvious place for monsters in fantasy fiction, fairytales and the like but, for me, the worst beasts are the ones that don't look like they are. The slimy, the snide, the con artists who happily destroy others due to their own greed - those are the real beasts as far as I'm concerned. And I'm far more likely to come across those than something that is clawed, fanged and not after the vegetarian option in life!
Whatever kind of beast you do portray (from the obvious monster to the less obvious type), what made them that way? Were they driven to it by the way they were treated or just out and out evil from the start? When they come across beauty, do they covet it or try to destroy it? Who are the real monsters in your stories?