Yes, traditional names (although I'd suggest not going so traditional that you label them in Kanji or saomething). Western equivalents wouldn't seem right, and how many more people would know the D&D versions anyway? You could, however, include a separate image with an armoured figure and labels pointing to each of the relevant parts, for those unfamiliar with the terms who, like me, sometimes find thumbnails a little too small to be entirely sure what they're showing.