For what it is worth, if you check out the joint Obama/Biden campaign pictures on the official campaign web site, you see that Biden is usually in the background a bit (except for one style of campaign button). Always, when their names are in print in any item in their store, Biden's is in a smaller font. [By the way, is Obama getting more grey hair? Or is this photo below - header of the campaign web site - meant to look that way to give him the appearnace of more experience?]
Palin enjoys a little more prominence in campaign buttons and photos. She is usually pictured alongside McCain or at least a similar size photo. For store items, her name is usually in the same font size (with the excpetion of one lapel pin).