A great map book would be cool
Lots of cities, historical Hyborian maps (Acheron, Stygian Empire, non-Kull, etc.), ruins, pirate bases, extents of tribal wanderings of Zuagir, significant river tributaries, vassalage markers, military encampments, forests, cave openings/hideouts, swamps, a location for Atali's frost giants, Aram Baksh's place, wandering pattern of conan (big map with little red dotted lines), cult locales, a brief sentence or two on each location (if not previously covered), etc.
It would take a bold person to move towards "saying" where stuff might be however. A simple disclaimer for purists who know their stuff might read "These are estimation suggestions for gaming purposes; if they oppose any canon you can find, please discuss it on our boards."
Honestly, I dont think you can get any of it wrong...barring making Shadizar an underwaterworld that is
jh