Am I missing some spines or something on his back?

Yeah the Skulltaker has the same kind of spiky spine that the normal plastic Bloodletter has. The "bit" looks just about the same as well. You're right, it's actually missing.

Nice paintjob too. Traditional colors. I like to tone down the drybrushing with washes myself.. makes things a bit more smooth somehow. On the other hand the fire in his one hand is really well painted I think.

After a saga worthy of Tolkien or Jordan I finally received replacement parts. Pic updated.

Definitely looks better now. :)

love the skull cloak, very very well done keep up the work bro