Masque

Masque is an add-on for World of Warcraft that provides a skinning engine for button-based add-ons. Note that you must have an add-on that supports Masque installed in order to use it. Masque does not support the default interface.

Extract the package to your World of WarcraftInterfaceAddOns directory.

Options
To access Masque’s options, use the /msq or /masque chat commands. You can also access the options via the Interface Options Window or by clicking on Masque’s icon in a DataBroker display.

Links
Mask Wiki
Masque Facebook Page
Get Skins