Most server mods have an option in the cfg that if the server population is under a certain number, normally 5 players, that it will go to a specific map or 2... I usually have this set to dust2, then when it fills up the normal voting kicks back in.
Also some mods will allow you to have 2 maplists, one for the mapcycle if the map just changes from one to another due to no vote or empty, and one for all the maps you want available on votes. if you set the empty/no vote one to just a few popular ones, it will just go between those til a vote sends it elsewhere.