By Tobias Carroll Even if you’ve never seen Ernie Barnes’s painting The Sugar Shack on the wall of a gallery or museum, you’re probably familiar with it. Its exuberant depiction of people joyfully dancing as a band plays also appeared on the cover of Marvin Gaye’s 1976 album I Want You, and it also featured prominently in the comedy Good Times. As for Barnes himself, the fact that his career included forays into both acting and professional football suggests that there’s a great biopic about him just waiting to be made. As ARTnews noted in a recent report on an auction at Christie’s, a retrosp…