Nokia has denied that the device shown was representative of an actual Nokia device and was simply there to compare Windows 8 UI across devices. The statement read:
This is a pretty reasonable response, because it's not like the webs were blowing up with speculation that Nokia was building a desktop machine just because there was a desktop monitor in the picture. Of course, we have to point out that denying that the image was a "Nokia specific product" is not the same as denying that Nokia is building or planning to build a tablet. So, you can take what you will from the statement.