Some time ago, I created a map of the ground floor of a haunted country manor for a D&D horror adventure. I created the map entirely in Photoshop CS 2. I devoted numerous hours, spread out over several months, to the project while we negotiated (ultimately unsuccessfully) with several publishers interested in the underlying adventure. The length of the negotiations enabled me to add details for which most commissioned projects simply lack time. (So here's a glimpse of what I do in the wee hours of the morning when I'm unaccountably awake and not obsessed with an ongoing oil painting project.)
I've gone back and recreated my development of the map, which I now offer here. I've designed this post-mortem WIP to walk anyone interested through the challenges I encountered wrestling with this piece. Nonetheless, this WIP is not a how-to tutorial on any specific aspect of Photoshop, although I'll describe my use of many tools along the way. To create a how-to tutorial, I'd do better to focus on a single room or individual effect. This thread presents a big-picture view of a major project's development.
Here's the finished map: