Born in Port Arthur, Texas in 1955 to an Auburn engineer father from Mobile, Alabama, and a mother from Dallas, Texas, Shepard has spent most of his life on the Mississippi Coast. He began fishing, beachcombing, sailing, and operating a small motorboat when he was eight and has been exploring and studying the coast ever since. He received a BFA from the University of South Alabama (1977) and studied at the Santa Fe Workshops of Contemporary Art (1976).

Shepard speaks a visionary language of deep ecology inspired by the natural history of the northern Gulf of Mexico and its disintegration at the hands of developers investing in sprawling overpopulation and exploitation.

In pursuit of complexity and visual interest, Shepard favors busy and frenetic compositions with an attention to spontaneous absurdity. He harmonizes the surface with bright, rich, pure colors. Influences for his work include many self-taught artists as well as ethnic sources from Pre-Columbian to African and Far Eastern parts of the world. His style reflects an appreciation for naive and narrative art expressed outside the restraints of the Western perspective. Among his traditional/contemporary influences are the art of Walter Anderson, the Post-Impressionists, and the Chicago Imagists.

He employs several media in his drawings. Many are on paper that has been darkened by watercolor — usually alizarin crimson, phthalo blue, and phthalo green. Since 2012, he has also been darkening canvas with watercolor and drawing directly on this traditional surface after applying pastel ground to give the surface tooth, necessary for colored pencils to stick. Since 2012, he has also been framing works on unmounted paper—without glass to cover it—by using a very thick 4-ply museum mount as the drawing surface not prone to buckling. The frames around these pieces are plain wood that he decorates using black ink and colored pencils.