While Tolkien’s denial clearly rules out the possibility that Tom is Iluvatar, I do not see that it eliminates the possibility that he is an offspring of Iluvatar’s thought, a Vala or a Maia, for I see nothing theologically troublesome with existence being a predicate of part of God.

Finally, there is Tom’s singing. Tom’s inability to separate song from his other activities, speaking, walking, working, suggests that it is very fundamental to his being in a profound way that distinguishes him from all other beings encountered in the trilogy. The wizards, for example, who are Maiar, chant (in the modern sense of the word) rather than sing, and never unconsciously. This continuous singing may be an indication of Tom’s high status. The world was, after all, brought into existence by a group of singers, the Holy Ones, some of whom became Valar. Second, Tom’s basic song is structurally related to Legolas’ "Song of the Sea" (Rings, 3:234-35), suggesting the possibility that Tom’s is a corruption of an original piece of music from the Uttermost West common to both. Third, Tom’s songs, although seemingly comic and nonsensical, have power in them to control individual elements and things in the forest. When told that Old Man Willow is the cause of the Hobbits’ problems, Tom replies, "that can soon be mended. I know the tune for him" (Ibid., 1:131), which I suggest means something like, ’don’t worry. I have the plans for that thing and can fix it right away." This is the kind of knowledge that a Vala, who sang the Music, would likely have, and singing would be the natural way to apply it.

If we take Tom’s remark quite literally that he "was here before the river and the trees. . .the first raindrop and the first acorn" (Rings, 1:142), he is saying either that he was in Middle-earth when the Valar arrived or that he arrived as one of the Valar. His remark that "he knew the dark under ths stars when it was fearless - before the Dark Lord came from the Outside" refers to the time before Morgoth, the original Dark Lord, had officially turned renegade - the time when the "old" or original stars were made. Since the world was incomplete at that time and nothing lived on the earth except the Valar, it is hard to believe that Tom is anything but a Vala.

Because most of the Valar are married, determining the possible identity of Goldberry can be a help in establishing Tom’s. There are three possible Valier who might have enjoyed living for a time in the Old Forest: Nessa, Vana, and Yavanna. Nessa, who loves deer and dancing, does not fit too well, since neither of these is Goldberry’s specialties. Her husband, Tulkas, the best fighter among the Valar, moreover, is probably too warlike to be Tom. Vana, who cares for flowers and birds, also does not fit very well, since Goldberry is concerned with a larger variety of plants, and birds have no special role. Orome, Vana’s husband, furthermore, is a hunter, especially of monsters. If he were Tom, there would have been no wights on the Downs. With Yavanna, however, we have just the right emphasis, for she is responsible for all living things, with a special preference for plants. Since she is Queen of the Earth, it is easy to imagine her watering the forest with special care, as Goldberry does during the Hobbits’ visit.

Aule the Smith.

Ah, this question’s old as the hills...or at least the ents.
Check this link: http://www.cas.unt.edu/~hargrove/bombadil.html
Tom Bomadillo...a very unique and different character, for sure.