He achieved success with his portraits and his Giorgionesque figure compositions, which are marked by a classic sense of style, and with his etchings and lithographs.

[10] Dublin Municipal Gallery owns several of Shannon's work, including The Bunch of Grapes and The Lady with the Green Fan (a portrait of Mrs Hacon).

One remarkable picture is The Toilet of Venus, once part of Lord Northcliffe collection and is now held at Tate Britain.

[10] [11] Later works by Shannon include The Amethyst Necklace (1907), The Morning Toilet (1911), The Embroidered Shawl (1914), and The Incoming Tide (1918).

[citation needed] Complete sets of his lithographs and etchings were acquired by the British Museum and the Berlin and Dresden print rooms.