Hi. Collaboration is very cool, especially for me since the area I live in is almost completely devoid of people into this sort of thing. I would say I am a better writer than cartographer. I usually start my worlds with a quick short narrative, then go from there.
Having said this, and not really believing my maps are up to par (compared to the high quality I have found on this forum) I would propose any maps I come up with most likely be used as a rough guideline for the more skilled amongst these forums.
My two cents on collaborating.
Feel free to flesh out anywhere in the Beastlands to your heart's content, Perfect!