Who's making you settle for a 10 pager? I'm like 30 to 50 pages into my 250+ pager. With rejection comes FREEDOM!! And probably more rejection, but I'm not thinking about that...
But no matter how many pages you're gonna need for your setting, here's some things I'd suggest.
A little spiel on how your world works and how it is unique.
A listing of original classes.
A listing of gods.
Some new feats, skills, spells, etc.
A few legends.
Notes on countries, seas, and places of interest.
Just my 2 cp.