Shannon's paintings have been exhibited in many galleries[8] and museums[5] and are in the permanent collections of the Brooklyn Museum, the Corcoran Gallery (now closed),[9] the Hirshhorn Museum,[10] the American University Museum,[11] the Yellowstone Art Museum,[12] and the Museum of Fine Arts in Boston.[5]
His work belongs to the representational genre of painting. The paintings often address strong sexual, mythological, and narrative themes, and issues of sex and race routinely dominate his exhibitions.[5] The Washington Post noted that "...Much realism nowadays is pre-digested pap, easy on the mind, easy on the eye. Shannon will have none of it. His art prohibits delectation."[13][14] The Washington Post also stated that "Shannon is a masterful painter of the human figure."[5]
Hilton Kramer, writing in New York Times, notes about Shannon and his artwork: “… But he is what he is, an artist of some independence and much energy and a furious talent who has declared his independence of everything current esthetic opinion has declared possible.”[15] The New York Times art critic Grace Glueck also observed that "Mr. Shannon's brisk way of painting his urban grotesqueries - he gets it all down like a born storyteller without too much fuss over how - belies their disturbing content. They don't stay with you too long, but they do evoke our age of anxiety."[14]