If they go through your AW post sale checkout, the PayPal ID that will show is your mailstep ID. If you are inserting logos into your auctions and are wondering what happens when people click them to pay, I believe that you still need to enter in the seller's ID anyway so if you were going to do that then you could put your mailstep ID in the item description for the auction as your PayPal ID. PayPal has different logos you can put in auctions but if there is one that defaults to an email address, I think it defaults to your primary PayPal address.
