Scanning maps and converting them into a format understood by Maemo Mapper is possible, but not a trivial task. Search the forums a bit for how this can be done, but I wouldn't recommend it.

An alternative would be to use one of the WMS map repositories. I believe the Terraserver repository, for example, has topographical maps. You will need the "proj" package (available from the same application repository as Maemo Mapper) in order to use WMS map repositories.