With the PrefabInstancer, you can bring any 3rd-party object into the AX node graph. Simply add a PrefabInstancer to your node graph and then drag a Prefab from the Project window into the object field in the PrefabInstancer node. At this point, the Prefab should be appearing in your scene. You can now feed that into any other node in the AX graph, such as Repeater nodes and Deformer nodes.
For example, in the GIF below, a statue from the Asset Store has been added to a PrefabInstancer, which was then fed into a PlanRepeater.
A PrefabInstancer may also be fed into a Deformer. For example, in the GIF below the 3rd-party statue has been fed into a TwistDeformer.
Finally, Robot Kyle, a free model available on the AssetStore, has been GridRepeated with jitter to populate this arctic beach scene: