But if Blizzard would ever raise copyright issues it would be you who'd be held responsible. It's just a warning, wouldn't want you get into trouble. If it's a company that commissioned you, it's not impossible Blizzard would stumble upon your art.
It is quite hard to sue someone if you are dead, not to mention if the races don't have a perfect depiction anywhere, only in sketches and a few written notes in the books. Also, which one would you consider to be stolen? Elves? They've been changed more than enough to avoid these issues. Dwarves are from a different origin than in Tolkien's universe, and also look a bit different. Don't take the movies into consideration, only Tolkien's notes and depictions.
Oh man... I mean, seriously? [link] It's like you've putten it mirror-inverted and changed the color and the accessories. Like I said with the griffin of your gallery: Try to be more creative! It should be your unique work and style, not a wannabe look-alike.