Here's a conversion I did many years ago after I made that first squad of Grey Knight terminators. I took some generic space marine bodies, chopped them up, extended the legs and arms, and then did a whole lot of sculpting with brown stuff and green stuff.
That original unit won a gold Demon for 40K Squad in 2007. I made some other specialty characters like this one soon after. I sculpted the incinerator out of grey extra firm sculpey. The sword is a very old Grey Knight bit.
I did some other sculpey parts on the back, such as the vents. You can see the places where green stuff was used to get a finer detail...
Here's what the original WIP images of the squad looked like.
And the finished group!
I still miss these guys. Hopefully I will be able to recreate them one day.