I don't know if members are aware of this resource :
It contains copious photographic material from the 1878-80 campaign including many photographs that certainly I have never seen before.
On the home page there is a search facility. Select: Second A.-A. War (1878-1880) (170). Amidst the many landscape shots there are group shots of Royal Engineers and HQ staff groups as well as a few gunners, infantry and cavalrymen.
Alternatively click the 'Series' tab and you will find these options:
Royal Engineers Museum, Library and Archive
• RE 1878-79, Part 1: 001-056, Khyber, Jalalabad, Gandamak
• RE 1879-80, Part 2: 057-099, Kabul Photographs
• RE 1879-80, Part 3: 100-115, Confidential Photographs/Plans
• RE 1879-80, Part 4: 116-140, Bryan Maggs Collection
Warning, do not examine this unless you have a couple of hours to burn.