I am just putting out a quick post to say that I am working up a list of starting traits for various planes when playing Planescape under the Pathfinder rules. The traits are from a free add-on to pathfinder and you can download the pdf here: http://paizo.com/pathfinderRPG/resources
The rules are similar enough to 3.5 that you should understand most of what everything means if you don't have pathfinder but do know 3 or 3.5. There is also a free pdf conversion guide included on the linked page above.
Starting off I want to get at least 4 traits for each of: the primary 4 elemental planes, Sigil, and for each of the nine alignments as well as four prime-worlder traits. Eventually I'd like to expand to have some traits specific to most every plane but you have to start somewhere.
Generally, two traits are supposed to equal a feat. Characters start off with two traits picked from two different lists at character creation. Characters would not be required to pick a trait from any particular list.
Please feel free to post your own trait ideas below. I am going to do so, myself, once I've had a time to sleep and get some ideas written up a bit better.
What's most important are traits for each of Sigil's Wards, as it's the focus of PS in my opinion.
As for how traits work, I'm most familiar with how they were in the Second Darkness Adventure Path, I haven't looked on how they were in Pathfinder core rules.