many times these paint shops get new employees, or equipment, and they have to try out and experiment....so they choose appliances....mostly refrigerators/freezers...
some do a basic white or colors....experienced guys will do stripes or flames, into actual art....
my brother works at one of these places....I was getting a number of re-painted Fridges...all they wanted them for was practice...and they give them away after that...
a few fridges were painted and converted into Kegerators...