Not natively, however:
Via a GelaSkin.
I wonder if that even works properly. The back of the Kobo isn’t flat. As they like to point out, it’s quilted, which basically means lightly bumpy. How would that skin fit?
I went on Flickr hoping to see an example of one, and was led to this blog post: Kobo and the Enamored Owl. Seems to work out.
Here’s the GelaSkins link for Keep Calm.