Hi, I'm trying to find a small tool to generate basic 3d mazes for later editing. Does anyone know sth like that? Thank you in advance.

Interesting idea, so you start off with the maze and go from there. Couldnt you write it yourself? you could make it however you liked even uv mapped if you wanted. You could even hire someone to do it for you?

1) Look up roguelike maze generation techniques. Here is one with source, but keep looking until you find one method that suits you best.
http://www.roguebasin.roguelikedevelopment.org/index.php?title=Simple_maze

2) Open Blender, and make a few tiles. Make 1 tile for every unique part you will need.

3) Open the Python editor in Blender, and write out a script that will generate a maze using instances of your tiles.