I have a land-locked regional map (altitude false color with shadows) 250 by 444 km at 69.45m/pixel that I would like to change into a fantasy / steampunk regional map. Looking at printed maps what I want comes out to between 2.5 and 5 miles per inch. The map is going to be for online display, so I don't particularly care about the print-out, but I don't have a clue about how to scale information for online display.

In addition to standard terrain (hills, mountains, forests, lakes, marshes) the map will indicate cities, rivers, a variety of roads (including railroads, flagged and drained, graveled and ditched, and cattleways), cave entrances, and boundaries (counties, baronies, and the continental divide). It will probably include tourist landmarks, and hunting, fishing, hiking, and skiing areas, but I haven't completely made up my mind.

Any and all thoughts about what scale I should use would be appreciated.