Gojira, there are many types of meditation and what you describe about contemplating reality is one of them. Just thinking about a specific subject.
And you don't have to meditate to bring about hypnagogic imagery. Just go to sleep...as you already know. If it interests you any try to stay aware of these images as long as you can without drifting off to sleep. You may be amazed at how complex they can become and the scenes they can start to form.