You have no idea how jealous I am of your opportunity to take such beautiful pictures of such beautiful creatures. Personally, I wouldn't change the image. I love how soft it is but as you're looking for critique I guess I could come up with something!
The nose and whiskers would be the only thing I'd attempt to change. Bringing the darks in a little on the nose to give it more detail and perhaps bringing in the little hairs on the chin a little brighter like the main whiskers to bring them more into focus. It would be interesting to see whether that would give it more detail or if it would lose the softness I so love in this picture.
If you do try it out, send me a copy! I'd love to see how it looks
Oh and thanks for the new desktop image, this shot is just incredible!