Ian Marshall is a Fellow of the American Society of Marine Artists and the author of four books of paintings, Passages East, Armored Ships, Ironclads, and Flying Boats. His work hangs in the permanent collections of the US Naval Academy Museum at Annapolis; the Royal Naval Museum at Portsmouth, England; the Scottish United Services Museum at Edinburgh Castle; Maine Maritime Museum; Lloyds of London; Foynes Flying Boat Museum, Co. Limerick, Ireland; Botswana National Museum; and the Royal Netherlands Navy Museum at Den Helder, Netherlands.

For eighteen years his paintings have been shown in London by Oliver Swann. Swann's gallery, now merged under the name of the Royal Exchange Art Gallery and located at 24 Cork Street, is the only West End gallery devoted to marine art. In America Marshall's work is shown by the American Marine Model Gallery at Salem, Massachusetts, and the Russell Jinishian Gallery at Fairfield, Connecticut. His ship paintings have been the subject of public exhibitions at civic galleries in Portsmouth, Plymouth, the Edinburgh Festival and the Imperial War Museum in London. In the U.S., he has had exhibitions at the US Navy Museum in Washington, DC, the US Naval Academy and the Maine Maritime Museum. His work has been hung regularly at annual exhibitions of the Royal Society of Marine Artists in London and at the Mystic International, Mystic Seaport Museum, Connecticut.