I've played around with Wiki code a little bit, and in the process, created a few of my own Userboxes.

Code Result
{{User:Mr Minchin/Userboxes/User Canadian English}}
This user contributes using Canadian English.
{{User:Mr Minchin/Userboxes/User Pi}}
Pi ≈ 3.1415926535897932384626...
{{User:Mr Minchin/Userboxes/User Love Farmers}}
Love Farmers, They Feed You.
{{User:Mr_Minchin/Userboxes/User_Parrallel_Universe}}
This user feels like he's diagonally parked in a parallel universe.
{{User:Mr Minchin/Userboxes/User Crazy Frog}}
This user thinks that Crazy Frog is annoying.

I must admit that the Pi one is not my own creation...someone (or some bot) must of subst: it onto my page, so I just recreated it as a template. Crazy Frog was another one I found along the way.

The farmers one and the universe one are more bumper stickers than Userboxes, but it's fun to play and learn the wiki.