That this is done at Brady's studio is evident by the floor. If you have looked at as many images from the time period as I have by now, you learn to look at the setting first.
That's Brady's floor. I am not sure if it is a rug or a painted patch of flooring. I don't even know if there was linoleum yet (but I shall find out!). But that's Brady's floor. It shows up everywhere.
But, aha! Pray, Gentle Reader . . . what is the wadded mass of fabric upon which Our Soldier's booted and gaitered foot rests?
'Tis the foul banner for which brave Colonel Ellsworth gave his life! Our Soldier stamps his foot upon it, stained as it is with the Martyr's Blood!! (or some such Victorian silliness!)
But, it is the flag which flew over the Marshall House. It is the flag Ellsworth felt should be removed, never again to offend Union sensibilities.
Brownell carried this flag with him to every service given for Ellsworth, and bore it in parades/funeral marches on the tip of his bayonet--or at least one of them.
There is great mystery as to the provenance of this flag. More on this at a later date!
Another thing worth noting is the black armband tied around Brownell's left arm. It is a 'mourning band," worn by men who have experienced a personal loss though death. There were many rules and strictures applied to women during a time of mourning, but men were not expected to do nearly as much.
A man wore a mourning band on his arm for about six weeks, not more. Sometimes a black crepe band or ribbon was attached to his hat. Mourning badges or cockades were made for those who attended a funeral or wished to show sadness in the case of a figure of national importance.
The Fire Zouaves wore their mourning bands proudly, sadly, for Elmer Ellsworth. That Brownell would not remove his armband for a series of portraits gives an idea of its importance to the young corporal.