The cool thing about re-purposing a map from another source is that if your players have any familiarity with the source map you can use that to your advantage. Maybe the PCs should be familiar with the area and by using a base map that your players are familiar with, there is a stronger connection to your game. Of course you can use this familiarity for evil purposes as well. If you players think the can rely on their personal information to gain an advantage, then you can twist that aspect like a knife to stick it to them.
I'm not saying you should do this, just that you can.
This map is the edge of a small fishing village that is iced-in for the winter. There are a couple of buildings, some lower-lying areas, and even a couple of tunnels through the hillsides.
This map only took an hour or so to throw together, but I've spent hours (if not days) on this map.......click here for the hi-res version.