From polymer clay of course!
In my classes we do a variant of this – and of sugar cookies – every year. Piped icing, cookie cut outs and a little originality makes for adorable, fun decorations. Robin Wiesneth makes this version. The only improvement I’d say is if you have an extruder use that to pipe out your icing.
Also if you want your ornaments to have a bit of the gingerbread smell for a while… mix in a little of the spices used in the cookies or a bit of vanilla extract.