Usually, Deutsche Bahn offers a map (Streckenkarte) of various regional transport similar to this one for Baden-Württemberg. Could anyone let me know where I can find it for Berlin-Brandenburg ticket? Also, maps for other regional routes would be nice. I want them as official maps either directly from the Deutsche Bahn or other trusted sources.
You can find these maps for all German "Länder" on this DB site.
The one for Berlin-Brandenburg is found here. You may be used to the other look of the maps (like the BW one you link to), but apparently this is the new look for Berlin/Brandenburg at least. You can find an out-of-date version (as of 2007) here if you insist.