we've just started looking at the tempest too.
so far the main things we've extracted are the concept of 'controlled destiny', the emphasis on sleep, music, dreams, art; the juxtaposition of Ariel and Caliban and what they represent and the presence of heaps and heaps of binary opposites.
We haven't got to the bit where we actually link it to imaginative journeys, but i went to HSC lectures on the tempest and my other texts and one guy mentioned five types of journeys. off the top of my head - 1. Dreams 2. Metaphor for Personal/Moral Growth and thats all i can remember.