Specialized types of regions and regions with neutral armies on it right from the begining. They could have been recognised by special background image. Even if player would take this field, background would look the same, just change color. Now as we have map editor it would realy nice and give map artists more ways of expresion.
Defensive region: silimar to reptiles bonus, defense boost or X % chance of holding ground even if lost in rolls.
Possible backgrounds: old brick/stone wall.
Possible usage: in in choke points with 2 or more fields connected from endangered side.
Offensive region: similar to arachnids bonus, offense boost or X % chance of wining an attack from this field even if lost in rolls.
Possible backgrounds: crossed spades, claws or some kind of weapon.
Possible usage: at backdoors of natural "bases" or middle of some areas where many players wight at once.
Increased spawn region: 2 instead of 1 troop per turn or +X % to total spawn per turn for every field under controll.
Possible backgrounds: small house, three balls in triangular shape.
Possible usage: middle of areas which players fight over, natural "bases" to reduce regions count required.
Teleportation region: region consisting of 2 or more separate, unconnected areas. Every part of this region whould show its own army counter, but would point the same data structure. Possible backgrounds: blank, color only, lighter/darker color. Could be limited to one per map to reduce mess. Or spiral galaxy bacgrounds of few diferent kinds which would allow identification which teleport leads where.
Possible usage: connecting middles of few big areas, nicer looking solution for "connector" regions (like world map)
Increased troop region: would allow to put max 9 or 10 troops on this field instead of default 8 which would give additional atk/def bonus as well. Possible backgrounds: some kind of fortifications, balls in triangular shape, north pointing arrow.
Possible usage: choke points or middle of the map.
X turns block region: could not be claimed untill X turn
possible backgrounds: dark gray.
Possible usage: walling of some parts of map fe. to let everyone prepare for epic clash or to ensure spread of players in first turn (blocking face-to-face placement on user maps).
Neutral armies regions: could not be claimed right from start cause of some troops already there. Touching it on "borders" distribution would force units placement in this point (strategic meaning).
Final notes:
Random maps could contain those kind of fields but if so it whould be optional (Special regions: yes/no)
EDIT: Those special teritories should also be "locked" from choosing as starting position or should start with 4-8 neutral armies on it. On "full map" those should always be neutral.