I think these are pretty close to MERP art and to what I imagined Orcs looked like when I was reading The Lord of the Rings, which was my second encounter with them.
HeroQuest was the first, go figure. The difference between both versions is basically the green skin vs. black hair/fur. The build and facial features are not too far apart.
By the way, you refer to
Baylor_OgreBane wrote:the old celtic folk lore
as a starting point for the literary evolution of Orc.
That is wrong. Toliken took the mere word "Orc" and tagged it to his completely invented race. So, the word "Orc" as in pre-Tolkien folklore is not attached to ANY interpretation or description of post-Tolkien fantasy literature.
Thus, the evolution of the Fantasy literature/game Orc begins at Tolkien's version.
Basically, there are two directions: the hairless, muscular, heavily caricaturesque version of Games Workshop (since ca. mid-90s), Rackham's Confrontation, World of Warcraft;
and the less extreme, more naturalistic heavily hairy, ape-like version of Tolkien, Das schwarze Auge (The Dark Eye), and Dungeons & Dragons.
Not I think I've written an essay like this before in this here thread. Well, I didn't look it up, so you can look for inconsistencies...