I tried it out, and here's my thoughts in the order I thought of them.

- In your readme.txt, you mention "I wave the copyright to the full extent possible CC-Zero"
- To me, this makes it sound like everything in the .zip is CC-Zero. That is probably not what you were after, atleast I hope not.
- My skyboxes are licensed under a CC-BY-SA license, which you failed to mention.
The textures seem really large in file size, and if the map is eventually included, they'll probably be compressed a bit (That's what happens to my skyboxes anyways)
- The folder structure, while it works, is not how things for Cube 2 Engine games have been in the past. Take a look at the Tesseract/media/texture/ folder. The subfolders are either online names, or the websites they came from.
- My skyboxes, by the same convention, would be in Tesseract/media/sky/penguins/
- I also ask that you include my readme.txt (or its contents) http://www.freezurbern.com/files/skyboxes/readme.txt in the folder with the skyboxes, or in another reasonable place

Besides that, I only found one error in the map (I boosted the brightness of the screenshot btw)

Sorry for nitpicking, but the map still has a licensing problem.
Read the license of cgtextures once more as you certainly can't license them as CC0. Always care about licenses as they care about you as well.
There may be a nice reference to the website of the models, but there still is no proof you actually took them from there. Where's the original link to the models?

The models contain way too much vertices (the skeletons have 8128 vertices, an ordinary playermodel isn't even using that much vertices!). So lower the vertices up to 1000 (like all mapmodels have). This counts for the lantern as well (as it has 1286 vertices; a lot for just a lantern).
If you don't believe so; start up your map, go into edit-mode, then execute wireframe 1 and thirdperson 2. You can compare the skeletons (and lantern) with the playermodel easily that way.

There is also a skeleton floating inside a wall...

The content provided within the map is great, if the licensing would be fixed.

The map itself, needs some more care. Only the mapmodels make it appear somewhat satanic, but that's just it. Without them, it feels like an empty map with no theme at all. So I'll give you 2 points for the effort and perhaps some more if you fix the licensing issues. But next to that, work on stuff like details, texturing and even lighting as well (a sunset doesn't feel very right at such theme).

try to immerse the player a bit more.
Having a boxshaped map with only 1 type of border/limit (the fence) is not showing enough variety.
Add some roofs that point to the inside (like on the map memento from sauerbraten)
If needed, a bit of terrain. The church tower outside of the playable area is a nice beginning :)