For this campaign, we created both Mobile and Liquid Desktop Skins.
A mobile skin is the same as a desktop skin but also includes a footer ad, and formatted for the small screens. It is image-based and contains CTAs.
A liquid skin ad (also called a background ad, a site takeover ad, or a bookend ad) appears in the background on both sides of the web page, and header - wrapping around the page and is clickable. Uses imagery and CTAs to attract interaction. It can host a video as well.