Mick, you might consider the Ogden/ Salt Lake City area for you depot location. UP, SP, DRGW, and WP all passed through or terminated in one or the other. The architecture however may not suit your tastes as it does further west. For bridge/water locations, I suppose it depends on how grand the bridge and crossing need to be. There are any number of deck girder spans over various creeks and the Colorado River, as the DRGW heads west from Denver. The UP features two pairs of rather iconic bridges (one set of through trusses, one set of deck trusses) in Weber Canyon east of SLC. And there is at least one through truss and one minor deck girder span along the WP on the Feather River Canyon that I can think of. Of course there is Keddie Wye on the WP, but as a very famous scene it may not be generic enough for your needs. I can probably get map links or coordinates for you if need be. Or point you in the right direction at least. I like rhrough truss spans, but I now tend to prefer deck girders for photos. Through trusses are more visually interesting, but they obscure the interesting train thingy that's really why you're there in the first place. Deck spans of course don't suffer this issue.