Good suggestions on both counts. We do provide the "states.gpx" file for the navigating around the country, but a basemap would be even handier. It will take some effort to get this going but I think it is well worth it.
Lower/higher tilesets is another idea that we haven't revisited for some time. It would be useful, but with highspeed connections (at least ours) the tiles fill the screen almost instantly and waiting does seem to bother me. This is on the todo list, I think, but is not high priority at this point. A basemap would be better.