I don't have the expertise that you or the regular "posters have" but I really have doubts now that that flag is the blue regimental. You and I know that photographers then and now use props and arrange things (ex. Gettysburg) This flag could well be another flag used by the photographer or as Gregg stated, a wacky personal flag of Custer. And again it was 9 years earlier....who knows what he carried then. But as Gregg stated we will never know. I do personally believe however that the yellow fag was not at the LBH...it was the blue regimental, packed or not. Paxson may have painted it in either using the yellow type common to cavalry when he painted (he even could have looked at this photo!....Notice the eagle in this photo is alot like the eagle in his painting and not a regular regimental eagle...as Gregg said, the wing is a little off!) or this was a flag he saw that was in existence at the time he looked at the things available....coupled with stetments of other parties.
Philip Duer