I like the idea of Tom Bombadil being Eru Iluvatar. And the (very) circumstantial "evidence" can be compelling. That "Tom Bombadil" and "Eru Iluvatar" have the same amount of letters could be complete coincidence, however, Eru (the name) means "The One" or "He that is alone", and when Goldberry is asked about Tom's history she replied "He is"; also Iluvatar signifies "All father", therefore "fatherless", as Tom is also described. Eru uses music (and song) to create Arda, introducing the Ainur to the music of creation, and Tom, most assuredly, has power in his songs, banishing the Barrow Wights with songs and telling Old Man Willow "I'll sing you a song that will chill your marrow". It's nice to think that the, non-interfering, creator of Arda has found a little patch on part of his creation that he can keep, and tend, as he wishes. What ever Tom's history- creator, nature spirit, or gentle aside- it doesn't change the fact that Tom is my favourite character in LOTR, and the chapters with Tom and Goldberry, in my opinion, capture the beauty of Tolkien's universe.