Here are the wallpapers from the new Nexus 7 that is now available for pre-order and was shown off in full detail yesterday. From what I can tell, there is only one really new wallpaper compared to what came with the previous Nexuses, and it's the one that the new Nexus 7 comes with selected by default. I ran it through TinEye and Google's Reverse Image Search, and it's the only one that returned no existing hits.
Update: The 2013 Nexus 7 got an OTA today, and the wallpaper we saw on the box is now included. You can download it at the bottom of this post.
And here's the second unique wallpaper:
Another wallpaper of interest to me was this one below. I've never seen it before, and reverse image search brought back results from a small number of obscure places. I checked the N4 and the previous N7 but didn't find it there, so I think that while not entirely new, it's something most of you haven't seen (Update: Previously present on the Galaxy Nexus and the XOOM, but not seen recently - thanks, Huw and Rodrigo):
Here are the thumbs for the rest of the wallpapers - as you can see, most of them should seem familiar.
Download the updated full 38MB pack here: