At the moment the constructs I'm using are from my old skeleton army.
Large constructs:

Old Ral Partha Bone on the left & Crucible Bone constructs middle & right.
Medium constructs:

GW plastic skeletons, they use to be part of a berserker skeleton unit in my old army.
The middle one is my favorite, he has a flail-tail that you can't quite see in the photo.