Faerun.
map, and not .tga? And when does the game say that?
Still, I guess it simply means you do not have the appropriate Faerun.map in your maps directory. Either the .map and the .tga do not match (in which case, you should rename something, if you have a Faerun_small.tga and a Faerun.map, or the other way around), or you didn't download any .map file to go with Faerun.
This will be a bit more annoying, of course, as you may need to create your own .map file. I have four different .map files for the small Faerun, and Mosehansen Faerun may use another one, and... Anyway, what sort of .map did you want? No special provinces? The mundane Faerun, with all its special provinces? Something else altogether?
The .map files I have myself for Faerun are those ones:
http://www.dominions-2.org/downloads...l_mapfiles.rar
Note that those files call for a Faerun_small.tga file, and not Faerun.tga, so some renaming may be needed.