Here is a list of the userboxes I've created so far.

Code Result
{{User:Duonaut/Userboxes/Skin Modern}}
MODThis user uses the Modern skin
Usage
{{User:Duonaut/Userboxes/Skin Modern-2}}
MODThis user likes the Modern skin
Usage
{{User:Duonaut/Userboxes/Skin Vector and MonoBook}} Usage