Jay, my images are supposed to replicate a yellowing due to time rather than the brownish sepia tint. Also, sepia was a chemical process used during the photo processing rather than an effect of aging:
Beginning in the 1880s, sepia was produced by adding a pigment, called sepia, made from the Sepia officinalis cuttlefish found in the English channel, to the positive print of a photograph.
Sepia toning is a specialized treatment to give the photograph a warmer tone and to enhance its archival qualities. Chemicals are used to convert the metallic silver in the print to a sulfide compound, which is much more resistant to the effects of environmental pollutants such as atmospheric sulfur compounds. Silver sulfide is at least 50% more stable than silver.
The 'glow' I used was supposed to replicate the look found on some high contrast images that have faded over time leaving little detail in the highlights. Of course, what I visualize in my mind may be 180° off from reality.
I agree with you on the high quality of many photographs taken during the civil war period. They were extremely sharp and had a very wide range of tonality. Of course, I've also seen many that have fared worse for the wear over time.