After completing "No One Escapes from Cidhna Mines", Thonar Silver-Blood's body was resurrected and turned to an ash pile before I tried to loot it. I was just wondering if there were any unique items to be had from him or not? Because all that was on the ash pile was some clothes and boots, neither of which he actually wore from what I remember. He was wearing Fine Clothes, but those weren't on the ash pile. I'm not even entirely sure it's Thonar, but it's the only ash pile in the city, so I have to assume it is.

Any help would be appreciated. I'm a bit OCD, and it bothers me if I know I missed some unique loot. ;

The ash pile you see is either Thonar, or of the random corpse in the water. With clothes and boots, it sounds more like you found the ash pile of the random corpse.

In any case, even if you do find Thonar's ash pile (which will never expire, even after Markarth and the Reach reset,) it won't have unique loot.

What Sandslice said, but Thonar doesn't have any unique loot. Just his set of Fine Clothes/Boots, a piece or two of jewelry, the usually spoils from looting the rich NPCs.