You could do:
The Space Shuttle Missions:
Discovery, Challenger, Atlantis, Enterprise, Gemini, Endeavour, Mercury, Apollo
You could do Dreamy words(Note, Dream Allstars of MD uses a similar theme):
Fantasy, Illusuion, Mirage, Reverie, Vision
You can do motivational dream words,
Inspire, Amaze, Believe, Achieve, Aspire, Wish, Discover
And finally going of the Greek/Roman Gods:
Athena, Venus, Apollo, Zeus, Poseidon, Hera, Juno
And I like the mentioned idea of Greek/Roman Gods:
Apollo, Venus, Athena,
You can do the planets:
Mercury, Venus, Earth, Mars, Saturn, Jupiter, Uranus, Neptune, Pluto