Probably worth noting that there was actually no such thing as RFC 74 Squadron by the Summer of 1918, as the RFC became the RAF when it merged with the RNAS in April 1918. But that aside, a book with quite a few decent pictures of 74 Squadron in 1918 would be: 'Mannock The life and death of Major
Edward Mannock VC, DSO, MC, RAF', which is written by Norman Franks and Andy Saunders and published by Grub Street (ISBN 978-1-906502-12-6).
It's not a bad book actually, although it could have delved a little deeper than it does. Nevertheless, it is a good general analysis of Mannock's life, who was of course instrumental in the success of 74 Squadron, so 74 features a lot in its pages, as do pictures of the men and machines of that squadron. Needless to say, Mannock had left 74 by the height of summer 1918 to command 85 Squadron, replacing Bishop, but his time with 74 is close enough to cover the period you are interested in, so I reckon it's a good shot. I just had a quick count of the pics in that book and there are I think eleven pictures of men and machines from 74 Squadron, the rest of the pictures concentrate on 40 and 85 Squadrons which Mannock also served in.
Al