I'm sure I don't have to say this but this piece is wonderfully done. What I love the most out of this piece would be their pants, I kid you not. The folds are where they should be and are nicely defined.
While this is gorgeous, there are a few things I would like to suggest.
Something that I noticed is that Light's body area looks rather soft compared to his face. It doesn't look like there aren't any dark shadows in his body like there are in the face. Maybe add some darker tones in there, it will also help define some of his muscle features a bit more.
One other thing with his skin is that it looks like his face and body have two different skin tones. His body has a little warmer skin tone than his face.
The necklace with the three beads that Light is wearing, while it is nice, it seems like it doesn't necessarily need to be there. It's a little hard to notice at this moment. Darkening the chain/string and adding some darker shadows may help bring out that necklace more.
Also, with Light, his wing looks darker than L's. Maybe brighten that up so it matches with L's or so that it looks more noticeable. It also looks like it's blending in with the wall too.
The blue glow around L is a nice touch. Really shows out his angelic side. Also the two light sources must have been hard to work with, but you made it look like it was a piece of cake (which I'm sure L would enjoy ). What's great is that the yellow is a very nice golden color and it's easy on the eyes.
Overall this is still a wonderful piece of artwork. I was going to suggest the apple and their faces, but it seems like someone else has mention them so I won't say anything.
This piece is absolutely stunning. Before I begin,let me say that I am simply AMAZED by this work of art,and could probably could never create something so gorgeous. The wings in particular are simply outstanding! The faces are perfect as well. That being said,the legs on L look just slightly off,not enough to really notice right away,but that's a difficult pose,which I myself am not so great at,so it's understandable. Also,the necks look a little short and thick,but that might be the angle. And I agree that the apple seems a little flat,without quite enough depth to appear round. The background is stunning however,and overall it's a WONDERFUL rendition of my favorite opponents from Death Note....=^_^=