As you'll likely be aware already @aulyre, there's a vast and still-growing literature on the archaeo-historical aspects of the region, and you could easily spend years simply wading through as much of that as you'd care to - I have, certainly, starting back in the 1990s!

Of my own maps of this region, I posted a selection just over a year ago on the Forum here. Unfortunately, this was shortly before the Forum underwent a major revamp to its current incarnation, so the post now looks rather a mess, as we had to embed images rather differently then, using an "[Image_12345]" coding notation, but the images are all still there, just no longer where they were meant to be in relation to the text, so you have to hop up and down to get the full gist properly.

As for references, a couple of atlases I found extremely helpful when I was starting out might be of interest, if you haven't come across them yourself as yet, and a couple of texts.

• Michael Roaf's Cultural Atlas of Mesopotamia and the Ancient Near East (published in 1990), which I was thrilled to discover on checking this evening is NOW FREELY AVAILABLE TO DOWNLOAD COMPLETE (!!!), and with a string of appended corrections, thanks to the kind offices of its author, via the Academia website, as of 2017! Link. I think you will need a (free to join) Academia membership to download the full PDF, but that isn't too onerous. For all its date, it is an astonishingly inspirational work in my opinion.
• The Barrington Atlas of the Greek and Roman World edited by Richard Talbert (2000), which unfortunately isn't available online yet, though it is available for iPad as a download (as of 2013). Otherwise, the hardback version is available to purchase alternatively, which I think still comes with an additional CD-ROM, according to some comments I found online (the library copy I borrowed more than a decade ago had one), including this Wikipedia page, although some of the links from that are now broken. GBP prices (brace yourself!) for the hardback start at about 265 GBP (Amazon UK lists), but the iPad version is a less fearsome circa 15 GBP instead (albeit you'll also need an iPad, so swings and roundabouts...). The Princeton University Press pages for these are here: hardback version -- iPad version. The related Ancient World Mapping Centre website is probably worth a visit as well, albeit they've been having major site issues this year, so a number of links don't work currently. Most of their Free Map pages are still functioning, however, and are certainly worth a look too. The Atlas is another astonishing work, if for a somewhat later period than Roaf's text.
• Civilizations of the Ancient Near East edited by Jack Sasson (1995) is a monumental four-volume collection of specialist essays on all manner of topics for the region. The length and quality of individual contributions can be variable at times, but it is a wonderful means to find out at least some basics on a vast array of topics, with follow-up references to help get you started looking for more. Irritatingly, I can't even find an online description or a complete review of it, though I suspect barring extreme good fortune, it will mean accessing a library copy now anyway.
• Ancient Iraq by Georges Roux (1993) is probably THE classic single-volume introductory text to the region and period. It is, incredibly, and despite its date, still currently in print! You can also find it available to borrow or purchase via the Internet Archive here (limited preview version otherwise).

This has taken a lot longer than I'd expected to compile today, so I won't try to say more; there's enough to be going on with already, I suspect in this little lot!

Great-looking map now! Do we also get the Undercroft map at some stage?

Probably too late, but that's a big kitchen for just four people - three acolytes and one high priest, counting the beds. As there isn't a refectory-equivalent, maybe there should be some chairs and a dining table in the kitchen as well? And maybe also a door to the outside, as the route in means bringing all the food through the chapel.

Not sure about the off-axis Great Frog statue in the chapel alcove, given such things tend to be the focus of worship, not quite so tucked-away.

Maybe switch the secret treasury entrance to the passage nearer the high priest's chamber, rather than in the too-accessible chapel?

And what do the folks here do for lighting (no windows)?

Looking a lot better now!

Yes, I think the walls would work very nicely for ruins too.

If the stepped outer surface was full regulated, it would also work for buildings such as ancient Mesopotamian temples, which had deliberately constructed outside walls that had this kind of "vertical recesses" patterning all round them. I've had to draw these before, both by hand and on computer, and it can be pretty tedious for a larger building plan!

Is the structure intended to be open to the air, or is it meant to have a roof? The internal shadows work nicely for the first option, but not the second (internal wall shadows are too strong). Also, the interior doors appear to have no shadows.

As this isn't a dungeon, some of the structural features don't work too well. The two enclosed spaces without access-ways need rethinking, as do some of the wall-narrowings where there are doors. They're both abnormal constructions because they're wasting building stone unnecessarily. Now you might say that the layout has to be this way for religious reasons, which would be fine, though in reality, things like the enclosed areas would end up with at least some rubble in them, and a lot of plants growing there, unless someone goes in very regularly to clean them out. By climbing over the roof or along the walltops, down and back, lugging everything they've cleared away with them. So not a popular job then...

The group of trees seems oddly lonely, unless there's some specific reason why there are so few in just one spot. In a swamp setting, that really wouldn't be likely, again, unless someone's deliberately, and very regularly, clearing the other greenery away.

That 22-foot Roman Empire map is the Peutinger Table, aka Tabula Peutingeriana, and the Wikipedia page includes a high-res complete image of the whole - may take a while to load, however, as the full-size JPG is about 15 MB. This is the direct link to that Wikimedia image.