Well I took some advice (read: completely stole) from the Space Wolves Blog on how to build a Rune Priest, and I'm pretty please with the conversion.
I stuck a Plasma Pistol on him because I figure with Runic Armor, he'd have a small chance of killing himself (although with Living Lightning, he probably won't be shooting much). The ax is a kitbash. The stupid ax from the Space Wolf Pack box has two hands on it, so I took a thunder hammer and did a head swap. Speaking of head, the head it comes from the Terminator box.
I don't know if I'll make a fourth Rune Priest. They are fun to make, but I am getting low on extra bits laying about.