Update (Sunday, 7:30 PM): The Toys R Us website just posted an image of the wall clings, as you can see below. Click the thumbnail for a larger image. Thanks goes to Tropius Rider for the heads up!
Toys R Us employee Tor-Chic has informed us that the Black and White preorder bonuses will be Reshiram and Zekrom wall clings. Gamestop will probably give out the same bonus as well since the two stores have had the same bonuses for the past three games (a Dialga or Palkia stylus with Diamond or Pearl, a Giratina figure with Platinum, and a Ho-Oh or Lugia figure for HeartGold or SoulSilver). The February 6th Toys R Us ad will note the bonus, and if they include a picture, we’ll post it immediately.