There is an early photograph (or possibly a print) of the front range with the Francis Johnson castelations, but before the Victorian chapel was tacked onto the front door, I have a reference for it somewhere. There's also a good photograph of the later main arched entrance on James' Street, with flanking high walls.
Brookings print of 1728 shows the original (1701) appearance of the front building, the basement of which was excavated and survives, as shown recently on that 'Cities of the Underworld' or whatever, TV series.
Apart from that basement, the earliest buildings to survice from the complex are definitely that Master's House and adjoining industrial range on the western boundary, backing onto 'Cut Throat Lane'. These buildings appear on the first O.S. map (1847), but it's not entirely clear if the buildings depicted on Rocques map (1756) in a similar, but not identical, position are the same structures. The main house appears to have both early and late features, which could of course mean that it's an early house, altered later.
My earliest memory of James Hospital was of a large, campus style, green area open onto James Street, dotted with mature trees and criss-crossed by paths with little pointy signs directing you to the Eastern Health Board pre-fab where you got your E111 forms to travel in the EEC,
Back in the 80s I believe there was a proposal, by the architects who built the new hospital, for a very large 'Post Modern' gate structure for the entrance on James Street, that some staid review panel took great delight in cutting out of the contract, but I don't know if that's true or not.
These are the maps, I'll have a look for more stuff.
1847 Ordnance Survey map.
Early examples of re-branding are in evidence with the name of this institution continuously change over 200 years from 'The Poor House' to 'The City Work House', then 'The South Union Workhouse', and finally 'The South Dublin Union.'