Yes, Yes! Indeed. Kinda forgot about the pipes on the roof. oops..
But yes, this is pretty much exactly what I had in mind.
Just do all the detail once, then repeat ad-naseum.
I may be tempted to use a 128 * 512 for the uncolored part of the floor, but like you say - that's not the important bit, I wish I'd thought of color coding the image myself, nice one.
EDIT: Just the green and yellow bits - they don't have to reach from side to side. They're both mirrored accross the centre-line of the hall, yeah?
Edit#2: - Here's how I'd divide the texture up. (except for the pipes)
Resolution I'd decide based on how close I was planning to get to the walls and the resolution of the output device. Alex Alvarez has a good article on texture resolution, if you've not read it.