Current questions and answers regarding the map editor.

Is there a guide available on how to create new arenas?

Creating battle arenas isn't that difficult. It's all done through the map editor (at least, that's how I do it). If you're interested, I can write a sort of "homemade" guide.
By the way, I still can't figure out how to take screenshots in the editor. I know there's a "MakeScreenshot" button, but it only captures the working area, cutting off the window on the left (MapPropertiesTree), and usually, that's the window you need to screenshot.