As many of us have found actually quite a few references in previous KQ games a fairly obscure and not recognizable to the average player. In fact you have to go out of your way to discover were the references originate from.
As for Tolkien references KQ8 tried it already... That's largely were the Orcs came from... Along with other high fantasy archetypes in that game
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The twin snakes statue in KQ5 is also a reference to Black Watchers at Cirith Ungol, a gate into Mordor from Return of the King and the Neverending Story according to the Companion! Sam held up the Galadriel's crystal vial to counteract the deadly force from the statues eyes. This is actually one of the most direct concepts taken from Tolkien's story and readapted into the KQ world (rather than just adapting races from the books). It's also in my opinion a great example how Tolkien can be incorporated without feeling out of place at all!
Actually it really depends on what Tolkien works you are talking about the Hobbit is more fairy tale/children's story for example. Very different from his trilogy which was written for grown-ups (at least it mostly turned out that way). The Silmerillion would be even more removed, although it is quite mythic and legendary, and even biblical in it's own sense.
I don't say this in all seriousness, but rather than dropping a ring into mount doom, Graham drops cheese into a strange machine!
As for some mesoamerican stuff see desert in KQ7.
Other references in KQ8 are even biblical in nature, Lucreto for example is inspired by the fallen angel Lucifer, who attempted to be like God. The inspiration for the mask itself is a mix of Mesopotamian and Christian concepts. There is even a few references to the concept of trinity and the sacred number 7 made in the game. Don't overlook the bible as a source of inspiration.