Skinning Custom Control

I was trying to add a skin entry for a custom control that I made, but I kept getting the following error

"The control type 'ASP.controls_customerpicker_ascx' cannot be themed."

Surely I can skin my own control! After research, trial, and error I stumbled upon the solution that worked.

Adding the "[Themeable(true)]" attribute to my custom control class fixed my issue. Yippee!