We already got information about the mascot giveaway if you pre-order Open for Business from various shops. The official site has now published more details about this download. The mascot will be an outfit, and besides that you'll also get a life-size sculpture download to put outside your Sims store. The description below is from the official site:

"Pre-order your copy of The Sims 2 Open For Business today and get access to an exclusive Sims mascot outfit and accompanying life-size sculpture to display outside your Sims store! Give their business its own unique theme and mess with your Sims by dressing them as a wacky new mascot. The special mascot and sculpture display items are only available to those who reserve the game from their favorite retailers listed below. Get ready for your Sims bring home the big bucks in The Sims 2 Open For Business."

Instead of being available to the US only, it'll be available in various European countries as well. It's not yet sure whether it'll be available in the UK, and if so in which shops. You'll also get the downloads if you pre-order the pack from our PC shop (for now US only). You can also pre-order the strategy guide for extra hints and tips for the expansion pack.