Spare wheel cover
A spare wheel cover or spare tire cover is an accessory that covers the spare wheel mounted on external part of a car or van. On 4x4 vehicles the spare wheel is normally rear mounted and is often printed with a dealer's name or something more fun. Covers can be hard shells or soft vinyl covers. Spare wheel cover protects spare tires from the dirt and the sun's harmful UV rays in areas with many days of sunshine. Spare wheel covers need to be removed once in a while and cleaned. 
Jeep Wrangler spare wheel cover printed with a dealer's name
2015 Toyota Land Cruiser Prado with body coloured shell cover
Full size spare tire, with cover, mounted in cargo space area of a 1993 Jeep Grand Cherokee
1932 Nash Ambassador Rumble Seat Coupe with matching spare wheel with whitewall tire.
1994 Mitsubishi Pajero GLS. missing a cover.