Suggestions by @parkerc

Seth Green

as Reynold Greenleaf in Public Domain

Diego Luna

as Sir Bors the Younger in Public Domain

Domhnall Gleeson

as Sir Kay in Public Domain

Grant Gustin

as Alan A. Dale in Public Domain

Robert Pattinson

as Sir Palamedes in Public Domain

Himesh Patel

as Sir Gaheris in Public Domain

Finn Wolfhard

as Much in Public Domain

Tom Hiddleston

as Sir Geraint in Public Domain

Daisy Ridley

as Maid Marian in Public Domain

Tom Ellis

as Sir Percival in Public Domain

Scott MacArthur

as Arthur A. Bland in Public Domain

Tom Holland

as Sir Gareth in Public Domain

Michael Fassbender

as Sir Bedivere in Public Domain

Robert Sheehan

as Will Scarlet in Public Domain

Rami Malek

as David of Doncaster in Public Domain

Oliver Jackson-Cohen

as Sir Lamorak in Public Domain

Henry Cavill

as Lancelot in Public Domain

Will Poulter

as Will Stutely in Public Domain

Kit Harington

as Sir Tristan in Public Domain

Tom Hopper

as Little John in Public Domain