People call the Bay Area "Northern California", but it's really pretty central and it'll probably take even longer before Apple goes north for a name than it does to go south.

There are some good ones there too...Shasta, Lassen and Tahoe are all scenic (for the desktop background) and easy to remember. Other good candidates south (and east) of SF: Joshua Tree (already mentioned), Big Bear, Mammoth, Whitney, Buttermilks and Salton Sea.

Unfortunately, some of the parks in SoCal have names that simply won't work. Calling an OS "Death Valley" would be awkward and Windows already ruined "Mojave" as an OS name.