Get rid of the dark C4D behind the blue one.
Either take the ones on his shoulder out, reloacate them, or change the flow to match them. Regardless, they're all the same length, which is a little strange to look at.
Blur the shadow on the ground more, and lower the opacity to make it look realistic. Maybe even scale it out to make it wider.
To make the floor a little more realistic, on the canvas behind everything:
1. Fill with white.
2. Do some black soft brushing on lower opacity about 2/3 of the way down from the top of the canvas.
3. Copy the original white canvas over the brushing layer, and move it up a bit so that only the bottom half of the brushing is showing.
Simple wall-to-floor technique.
That will also bring your shadow out more.
Post your results after that and I'll see what else you can do.