Almost all map from dominions 2 can be reused in dom3
You will find list of them on the official illwinter site :
http://www.illwinter.com/dom2/maps.html
There's also Arryn site at
http://www.strife.com/dominions-2/files.htm#maps , and it inclue the Faerun map (also the dom2 version, there's an edited .map file for dom3 that has been done and can be found on this forum).
And of course this forum, and the dom2 map forum, are both good source, if you're not afraid to search.