These are the now unobtainable ( I believe) crew for the Imperial Guard.
I love the tank crew models. I believe there were rules for them as well at one point. If the Leman Russ took certain hits the crew could leg it and escape.
I also keep an eye out for the Valhallan models where they sit across the tank, much like what happened in WWII. I think GW missed a trick not producing crew and models to go on and around vehicles for all the different regiments. I think a lot of gamers and modellers would have snapped them up.