I think I have not yet figured out how to use namespaces properly. Previously I often created a namespace for enums, but it does create problems with names especially if you open the namespace. If you put an enum into class it's much safer that way, because it exactly ties the enum into that class. It also removes the need to add another namespace for stuff, which in large projects is important, because anything you add into the project makes it harder to maintain.
Currently I'm using more generic namespaces to store data and sometimes functions. For example there are low level text routines in 'codex' namespace and data in namespaces like 'creaturedata' and 'itemdata'. The data in Kaduria is often simple structs which again is probably not the best way to handle it, but it's what it is. The way I now see namespaces is more like a tool to keep track of data and not so much to isolate it from global scope which in C++ is a bit overkill anyway, because you can access only the stuff you include in a .cpp file.
I guess the "proper" way to use namespace is how std:: namespace is used in standard template library, which is to denote a super large library. But the way I'm using namespaces seems to work, at least it doesn't add more confusion.