As expert scavengers able to get into tight spots and out again with an armload of interesting bitz, Gretchin play a crucial role in Deathskull kulture. Being equally adept at nabbing shiny gubbins from other orks as looting mangled corpses, they help ensure the right components get to the right meks to construct the tribe's war machines. The Skulltakaz employ a considerable number to also help collect and clean the skulls that give the warband their name.
Da Bonepickaz:
About 20 years ago when grotz only came in monopose metal, I bought a box of WHFB goblins to convert into 40k Gretchin to bolster the ranks. I finally implemented my idea, using some small metal gun sprues that may have originally been from Necromunda, although I have long forgotten where I got them. The goblins are a bit bigger than the plastic grotz, but it ends up just looking like the natural variation in size in a highly variable race. The banners help convey the sense of large units and both use the skull/bone motif of the Skulltakaz.
I made 30 grotz and two Runtherds. In 4th Edition, you need one Runtherd per 10 grotz, so I could field these models as two units of 15 with one Runtherd each, or one unit of 29 with two Runtherds. This gives me some flexibility to field small mobs, such as for when there are many objectives all over the battlefield, or one larger mob that can soak up a fair bit of firepower before dispersing.
I painted them with a more yellow-green than the mossy-green of the orks, to indicate they are smaller, younger, and generally weedier than their brutish cousins. The Warboss in turn will have browner skin than the orks.
I was struggling to get good photos that show the colors accurately with my phone. I may have to invest in a proper camara with a lens and stand at some point.
Looking forward to seeing them out on a battlefield sometime soon, swarming all over a beleaguered squad of marines!