A transport network can include signposts and paths?
As an out-of-game thing, someone could create an imagemap for the png map, and make it display a preview (i.e. the images you linked to earlier in thread) when you roll over the appropriate area.
And yeah, a transport network can include those things but what I was getting at was that transport will not be its primary purpose (we've got that covered), it will be more of a tour-network.