I don't know if this will help, but the flag of the Blackland Gideonites was displayed in New York in 1864 for a Sanitary Commission fundraiser. A catalog of the objects exhibited during this fundraiser was published under the title Catalogue of the Museum of Flags, Trophies and Relics Relating to the Revolution, The War of 1812, The Mexican War, and the Present Rebellion (New York: Charles O. Jones, 1864). This catalog may have a picture or illustration of the flag - the Library of Congress has a copy of the book, it is call number E646 N62X.
I hope this helps,
Jeff