In what for a File can i rename my server?

I don't think you can, at least not where it doesn't show "Dedicated" to Gametracker.

The reason it shows "Dedicated" on GameTracker is because of the way Monday Night Combat dedicated servers work.
They always have the "Servername" set to "Dedicated".
But Ingame the part that represents the Server's name is actually the Gamename which on other games is like:

- Counter Strike: Source
- Day of Defeat
- Ricochet

etc...

I expect the servername can be changed in the startup line, because the way I remember it MNC works with *.bat files to launch your server, where the *.bat file contains all the server settings.