WallpaperLair.com has several wallpapers for many devices including the BlackBerry PlayBook, you can get the newly added BlackBerry Jam Americas 2012 one or another wallpaper. The download is very simple, so you can change thugs up on a regular basis if you want.
Cool thing about this wallpaper site is the ability to grab a wallpapers for pretty much any size device. You can also register/log in to the site, upload you own pictures, sharing your pics with others and use them as wallpaper for many device platforms. A short wait is needed for your uploaded picture to be approved, just to make sure it is appropriate for the site.
The Link to the Blackberry Jam Americas Wallpaper is Here. Just choose PlayBook for resolution.