I draw both what I see in front of me and what I see in my mind. I usually formulate an image in my mind and then find references either through photos or in the real world to help give better structure or a sense of reality to those imagined pictures. For example, I may imagine an angelic figure playing the violin - a lovely image, but I need either a physical example or a picture of someone playing the violin to make sure my angel and his/her violin feel "real."
Of course, sometimes scenes from this plain old real world are beautiful enough without any embellishment from me. These are also a joy to portray, and I do that often as well.