I'm not familiar with this particular picture, but I'm guessing that's Smaug? That's a good pick. The Hobbit was the first fantasy anything I can remember interacting with. I think I was in the 4th or 5th grade? It was a long time ago, my memory is really hazy. The Hobbit definately had a large impact on my love of fantasy. I can't say any of the artwork itself really stuck with me. Later on in the 6th grade when I read the Lord of the Rings some of the art there really impressed me. Most people focused on the art of people, for me it was the backgrounds and environments that stuck with me. I stuggle to remember any specific piece though. Since you brought it up I'll go looking through my old books and see if I can find one I remember really connecting with.
Nope, more faulty memory. My old books were cheap paperbacks that didn't have any art other than the covers. Two of the three books don't even have their cover anymore. I read those books multiple times and they're falling apart. I was probably mixing up some of my old memories of being enthralled with the world with art from later editions I've bought, or maybe the movie concept art. They did have the maps printed in them. I do remember looking at those and tracing the path of the Fellowship through the story. Thinking about what else was going on in world. Tolkien was massively influential on me because of the printed word, not the art. There are tons of great art out there of course, they just weren't very influential to me.