For the 2nd sig the shadow you added in yourself was a pretty good call to make the lighting more obvious. However, the light source still feels pretty messy. The render is a little misplaced because of the purple tone. Don't be afraid to use a gradient map to set his colour correctly. The render is also not blended very nicely into the background. That's all I have for now. It's nice to see a new face that strives to improves. Good luck.

i enjoy the background of the second 1
but as raiden says the render doesnt really fit with it.
so you could use gradient maps to change the render a bit
so that it fits better with the render as raiden says
or create a new background that fits with the render.
i see an improvements from the first sig to the second one