Ok I have now played through the first map and I am very impressed! It definitely achieves the old school feel that you were going for and includes plenty of impressive architecture. It took me about 35 minutes to complete (although I was taking my sweet time) so it is definitely not a short map, I think it has quite a nice pace to it and it kept me on my toes. I did however have a few issues with this map, the first being a hall-of-mirrors effect that I got in the area shown in the final screenshot you posted. I would also say that some of the monster placements became a little bit predictable towards the end and the ammo became a little too hard to come by for my taste, but these are just minor nitpicks in an otherwise solid map.
I look forward to seeing this project continue!