Is it possible to automatically create a reference node or entity with Rules? The idea is to have a node with information and an image Gallery reference. If the image gallery is clicked on the node view then it just shows the images with a link back to the original node. This way the original node can have one author while several different users can add photos. There isn't a need to populate the gallery on the original node creation since it will be an obvious second step view the node to add images or wait till later. I just think that it would make sense to have it available from the beginning even when empty.
The solution is to use the URL Node Reference widget.
I would use hook_node_insert() for this.