These days you can personalize things with photographs of people's faces. Not just t-shirts and coffee mugs but also things like jigsaw puzzles and even etchings on wooden boxes. So maybe do a search on custom/personalized photo gifts?
Also, GitHub did this thing where they used a 3D printer to print out replicas of someone's contribution history graph. I wonder if there's any way you could work with a 3D-printing artist to create custom replicas of the employee -- if not a realistic bust then maybe more like a bobblehead, or a Star Wars action figure where the head is customized to look like their own face?
I always thought a fun gift would be to have somebody's blog or Flickr stream converted into a hard-copy book. Not saying you should do that for employees -- but a fun precedent might be to come up with something super-personalized like that.
