Here are a few other possible themes you might consider:
* The dangers of passion when it leads to obsession; All three characters in Frankenstein exhibit passion that leads them to become obsessed with what they are pursuing passionately. Walton is pursuing fame and glory, as is Frankenstein, and the creature is passionately pursuing revenge.
* The effects of reading is another possibility; All three characters are seriously effected by reading. Walton reads about exploration and sailing; Frankenstein reads about natural philosophy and alchemy, and the creature reads about ancient civilizations, war, man's despondency, Christianity, and about his hideous birth.
*The effects of Parental Neglect: This is obvious when Frankenstein abandons his creation/son. The effects of this abandonment are clearly revealed in what the creature becomes, a sanguinary being.
*The Effects of Society: Society clearly has a negative effect on the creature; it turns him into a malevolent being. Society turns its back on the creature throughout the novel, all because of his appearance.
Well, there are plenty of themes for you to pick from in this amazing novel. One of the central ones is that of Birth and Creation. In giving life to his creation, Victor usurps the role of God. This raises all sorts of questions about the moral limits of science - just because we know how to do something doesn't mean that we morally or ethically have the right to do it. Just think of so many debates such as cloning or stem cell transplant where the dangers of "playing God" are rife.
Another key theme for you to think about is alienation. Both Victor and his monster suffer because of their alienation from others. The monster is an outcast not through choice, but Victor chooses to make himself an outcast because of the monster's crimes and his crime in creating the monster.
Lastly you might want to think about how the creation of the monster blurs the distinctions between the human and the non-human. In Gothic terms, this novel "plays" with the binary opposition between these two terms. To call the monster a monster is problematic, and yet it is clear that he is not fully "human."
You might benefit from placing this question on the discussion board and gaining a wide range of responses. Good luck though - this is a great novel with numerous themes, so I am sure you will do well!