A couple of other questions you might want to consider....

How old is the map? Can the characters read what is written on the map other than the "picture" stuff? What units of measure are used on the map and are they still in use by the characters?

Like the idea though. I suppose one way to approach it would be to have a cartographer (here perhaps) make you a sketchy sort of map with notes on it (something of their own most likely) and then hand it off to an artist to interpret (maybe yourself if you are an artist). Don't know if that helps, but maybe.