Hmmm ... it does appear as though he's floating a bit, and it may be because he is not actually touching the floor. But another part of the problem could be the shadow setting ... it appears a tad too softened and not as stark as it should be given that light. Another thing that you might want to consider is doing some postwork, to highlight the outer edges of the character more. To do this, render the image to a TIF file, so that it has an alpha channel. Then take it into Photoshop (or another image editing program that has layers). You should be able to select ONLY the figure's alpha channel, given that he is the only object in the scene. Copy the figure to a second layer, and then use a Dodge (or Lighten) brush to make the "backlighting" more drastic. For a good example of what I mean here, check out "Through The Rain..." in ToxicAngel's gallery. The bright glow on the left side of her body was probably done with this technique, and it adds a lot of drama to the pic.