I would like to have some options in the race section to distinguish human from different cultures. I would be interesting that the Varisian, Chelaxian, Shoanti... get something special, rule wise.
Yikes. That's a lot of cultures. I mean, Varisia is one thing--just the three flavors of humans there, but Golarion is a huge world! Now granted I think we're gonna' already get a huge helping of that in the Gazeteer. Huge from what I hear--they went a little overboard even.
That said, it would be nice to see races and cultures be a bigger than usual part of the Pathfinder RPG. Precident from the PHB gives a lavish peice of art to each class and a full writeup, usually a couple of pages. It'd be nice to see races the same kind of love in Pathfinder. Some of the races really do need it--gnomes particularly, but everyone could use it. Half-orcs are a whole different thing. Elves are really different. Halflings need fleshed out a bit. Granted I'll say the writeups on the various signature characters has helped tons--but lots of people aren't going to have read all that.
It'd be nice to see the cultures get a bit of notice too. The section in the PHB on making your character unique is really mostly an age and weigh/height table. It'd be nice to flesh that out with real backgrounds and background feats (like in the Forgotten Realms book). It'd be nice to fill in the equipment section too with some regionally flavored things to really flesh out the world and characters a bit--more stuff like the k'larr and earthbreaker. That way you've got solid options to make a character who really fits into his home region.
That's the stuff I really care about when it comes to making a good character that fits nicely in the setting.