i would back up fryingman here. when concentrating on a detail the detail gets more detailed ;P

in tonight's lucid i got lucid and the vividness was pretty dull. i approached a woman and looked into her face and with every second the face got more and more detailed until i could see every wrinkle and every nuances.
same in a later lucid that was not too stable or detailed. i started to fly right over the ground and chasing a guy and because i payed attention to the feeling of motion i could "see" how the details of the dreamscape increased linear.

and i agree with dolphin. how vivid or detailed a dream is has not necessarily to do with the lucidity grade because even though the details increased the lvl of my lucidity was pretty low, especially in the second lucid... after waking i had to notice that it was completely senseless stuff i did even though i was lucid

and i agree also with anotherdreamer when you can increase your lucidity you get more and more your "waking self" and therefore will remember your goals, for example to pay attention to your dreamscape and to details and therefore automatically increase vividness. when setting goals just "paying attention or looking around or examine an item" sounds boring on the first look but can be a very interesting and worthy experience!