TYP files are normally linked to one map ID (which can be found in the TYP file with TYP viewer) so I doubt if it is possible to create a TYP file for an already generated map containing several map ID:s.
So if you use an "pre compiled img" I think that you have to be satisfied with the TYP-ing made by the creator.
If you want your own style for tha map (which I almost always want for top maps ) you can always TYP the individual maps in Mapsource and then compile a new img.