Copplestone Castings (available through Northstar) have their beautiful 15mm Barbarian Heroes pack that looks like Conan in a few different outfits. They also have mounted Cimmerians, Cimmerians with bows, Vanir/Aesir and Picts, and there are plenty of 15mm historical analogues for other nations.
If your heart is set on 28mm, maybe em4 miniatures metal barbarians? I have some and they are very cool.
Those are brave men knocking at our door. Let's go kill them!