Have you ever seen a copy of the 159th's regimental history? I don't have a copy on me, so I can't say for sure, but if anywhere has any photos of the regiment, that would be the place. The book is "The 159th Regiment Infantry, New-York State Volunteers in the War of the Rebellion, 1862-1865," by William F. Tiemann (Brooklyn, NY: 1891). It's out in reprint, so it shouldn't be impossible to find.