Shield Maidens are tall, proud warrior women. The voice acting has been well made to suit their personality.
Shield Maidens are the troups you can summon via Siegfried van Niebelungen, from the neutral Ice faction once his meter has been "filled". 5 of those body guards will then appear.
The ice maidens are usually the most effective fighters in medium sized groups of +- 10 to 20. Unless summoned by Siegfried, where they can appear wherever you want >>> so you can open 1 gatehouse ... They do not really have a special ability, except ... If you call destroying the rose gardens unscathed a special ability?! That defence mecanism is not really used anymore in-game since version 1.2 of the Stronghold Legends game came out, which sadly makes this interesting character ... Medium at best, due to their overall statistics. Child Maidens are one of the few women characters you can play as, besides the agile flying white witches and the mighty ice queen.
For a fair price, they are the best to use at the start of the game to quickly protect important structures, like the granary or to protect the estates closely located to the headkeep. This will make it possible for you to cover them from swifter, sturdier enemies, like macemen with archers.
Same story, but for the estates farther away. If you still wish to use them, it's best to cover them with witches in conjunction with a small number of bears (specifically for chokepoints) or a medium sized white wolf pack you constantly replenish once some members have fallen (if a lot of units pass by). A group of maidens can thus overwhelm or protect/ cover a lord, swordsman or small to medium chokepoints relatively well.
Overall ... Macemen do most of the jobs better than them due to their shock tactics and lack of honor use, while the swordsmen that still use honor ... Are more interesting to use in case you cleared the archers and crossbowmen beforehand and wish to finish the enemy lord, protected by (a lot of) sturdy melee units in one single blow.
Remember ... You give honor to a melee troop. Honor is a valuable ressource. There are a lot of melee troops with the same function that do not require honor at all.
In short: it's more interesting to use honor for other niche characters, who have Another function. Witches and/or a single dragon can be used together, because in their case ... They are invulnerable to most of melee troops*, and with their own peculiarity, they give you a big edge in combat.
The edges: the dragon you can move, immobilises the enemies you wish ;
The witches, attack most melee enemies from above, without getting harmed.
*the men-at-arms is the only exception.