That's an interesting photo.
Left to right:
"H" van (grey, heavily brake dust weathered, snail)
GSWR open 3rd of about 1902-5 vintage, black'n'tan
Tin Van (silver; but for modellers beware - the roof is not black or grey - they were unpainted always - but it looks that way due to weathering and, remember, even then sometimes steam train soot / coal dust)
Tin Van, post-'55 green
GSR Bredin, post '55-green
Unidentified van - either early CIE or GSR mail / guard van (post-'55 green)
"C" Class loco, post-'55 green.
The picture is right at the end of the steam era, so a work-stained J15 would fit in well with the scene, as would locos of A, B121 (grey), B101, or early G class. Within a year, 141s would be a common sight.
Train make-ups then were not the boring fixed-set-of-same-type-of-stock that we've seen since the introduction of the Mk 2 "Supertrains" in 1972. Prior to that, it was very rare to get a train all of the same type of coach. Couplings were standard between all stock - something designers today have regressed on. It makes zero sense to have incompatible couplings sharing the same railway.
The above also shows that to walk between the only two passenger coaches would require a walk through not one, but two, tin vans. I encountered this once on a Rosslare - Limerick train, which had a van between two carriages, then another carriage, then another van. The van had cardboard packages of something or other in them and made for an unstable and noisy short walk from one coach to the next.....
For the benefit of modellers of this very interesting period, from recollection here are a few combinations on trains I remember travelling on. All were in the 1972-1980 period.
Rosslare - Limerick; as above, plus on another occasion a Dutch van, three laminates and a Park Royal.
Dublin - Cork; a Bredin, three laminates of two different types, two Park Royals and about three Cravens - all mixed up. A BR or Dutch Van was at one end and a six-wheel hot water bottle at the other.
Tralee line - a train with one Craven in between several park Royals and Laminates.
Loughrea - the one and only Loughrea coach, nothing else! Hauled by a "C".
Lisburn - Antrim; a "70" class set with the centre car being ex-GNR open 3rd 727*, the very last GNR coach in traffic, now unchanged from from GNR condition but in maroon and blue. Also, at the same time (1978, I think) one of the last MED sets had the last NCC coach in traffic, which I think might have been 526*. (* These were the UTA / NIR numbers. Original numbers were different). This last NCC coach had been externally repannelled by NIR in tin, but its interior was still old NCC with wooden seat frames. A beauty.