I think stuff like the tikis and ice-viking guys could work if you actually tied them into the Kremlings. It's negligible but your brain notices the industrial and polluted direction DKC's maps veer into as you progress closer to K. Rool's boss fight, and then DKC2 is a grotesque wasteland showing what happens when Kremlings get all the power they're after. Veer into that theme with something like Mad Max psychos/bikers with a viking motif.