I actually kind of do this when my sight gets lost after a lucid. I dive down to laydown on the cement. The 'darkness' you call it, is the void I seem to always go. If in the void, and you can't have a dream form around you, start thinking of any image you might have, and just concentrate. How many times have you been in deep concentration over something before going to sleep, then those words turned into pictures, and finally a dream? Countless for me (Those mostly are nonlucides). Just be careful not to 'fall' back to sleep (become unlucid).