A few weeks ago I used a big leg vacuum splint to immobilize a 2,5 year old girl who was hit by a car and was being carried around by relatives, head dangling and all.
The splint was the first thing within reach so I used it to stop those not so smart and panicky relatives from ruining her spine.
What also works well if you don't have the necessary bandages anymore for a dislocated shoulder : cut open the sweater or T-shirt a bit (with the permission of the owner of course ) and fix it with 2 kochers.
I have to improvise quite often unfortunately, the equipment is rather scarse sometimes .