Mayner, of this parish, is as I understand it, planning a model of this loco. Regarding the carriages, the first one (a lavatory first) and the second one (a 3rd) would be included in the subject matter of a recent post on MGWR six-wheelers as an essential part of the pre-1963 railway scene. Maybe the moderators could provide a link here to those posts?
The gist of it was discussion on how essential the standard MGWR six-wheeler is on any layout on GSR / CIE at any time 1925-63, and suggestions regarding kits, and Allen Doherty's very helpful Worsley Works "scratch-aid" kits. Given enough orders, he will make kits of these.
Thus leaves the next vehicle - a bogie 3rd, by the look of it - possibly a 2nd / 3rd. That would need to be scratch built from a drawing. If you're not that fussy about accuracy, there are some British SECR kits which could be botched to provide a half-reasonable approximation, though hardly worthy company for the loco kit and six-wheelers.
The fourth vehicle may be dining car No. 1, as the picture was almost certainly posed. In service, it is unlikely that it went beyond Galway. This vehicle was later rebuilt as a conventional coach. Again, if drawings could be found, that's the way to go - a complete scratch build is necessary. This vehicle would be the most challenging, as I am unaware of a drawing of it, and photos won't be plentiful as (a) it didn't stay that way for long, (b) few pictures of it exist and © I don't know of any other coach which might be botched to even approximate to it, let alone serve as a sensible donor.
Finally, the van. This is a Cusack high-roofed passenger brake, non birdcage. There should be more info on those, probably in the IRRS photos, though access to that collection isn't easy, even for bona fide researchers.
Overall, as the "Tourist Train", the actual train make-up would have varied; as mentioned in other posts, no train hardly - not even a special or specific one - ever had two carriages the same almost ever, prior to 1972 or so.
Livery was mid brown with yellow lining normally, but for a few years after 1905, and with all vehicles in this photo, a livery of royal blue and white, lined gold, was used by the MGWR. As you'd expect in steam days, white (not even cream) upper panels became filthy very quickly and they reverted to brown after only a few years. Indeed, it's probable that no more than a quarter of the fleet - if that - ever received this livery at all.
Some locos were painted blue lined in black and gold or black and white to match; others remained standard MGWR lined grass green.
The loco in this picture doesn't look pristine, so may be green rather than blue.