Agree, they are very nice prints - thanks for that link. They seem to have a very similar look and feel to them, so maybe commissioned by the railway?
I had another look through Michael Harris' "Great Western Coaches from 1890". He has some views of coach interiors (which are not always easy to come by), including various saloons. I took a few notes for possible future reference.
I think the photos illustrate (i) the diversity and (ii) that at least some stock series had the frames/prints specially designed to fit the interior (at least for the more prestigious/first class stock).
* Saloon Dia G3, built 1894: Elaborate curving frames around prints to fit below clerestory roof, p43
* Family Saloon Dia G33, built 1900: No prints evident (but may be behind photographer), p44
* New Milford Boat Train open Dia C18, built 1900-01: 3 prints on partitions, 2 different frame sizes, prints look similar to Buckjumpers link, p55
* Dreadnought restaurant car, Dia H8, built 1904. Prints and frames same as the one illustrated in my blog entry above (two prints per frame), P30.
* Brake saloon dia G58, built 1929: Small squareish frame, looks similar to Buckjumpers's link, p30
* Brake first saloon dia G59, built 1930: frames as above, but large, p32
* Super Saloon, introd. 1931 Large vertical (sic) frames, p86
* Corridor First Dia E163, built 1948: Prints embedded in compartment panelling. Very suave, p108