Cool. You’d do even better to have a full length portrait photograph. There is only one known example and it is in the MFA Houston’s collection.
This painting was painted in 1906 so it was painted from a photograph, maybe the one you are talking about. Sam is seated at a table and has his legs crossed. He is holding a newspaper and there is an early map of Texas on the wall behind him. There is one in the same pose hanging in the Houston Courthouse.
I’d like to see the photograph in the MFAH.