In response to your review request:
This piece would benefit from reducing the size. Shrinking the height down to the 2,500 px - 3,000px range would make the full scale viewing suitably large, but also not so large that when viewed at full scale little imperfections in the edges would show through.
You have some good color choice, but the shading can be more interesting, maybe putting some color into the highlights on the coat and boots, maybe a yellow or blue, depending on your feeling on the temperature. Getting some of that deep red toward the bottom of the background in the shading on the shirt and hair would help bring some more unity in to the piece.
Th shapes and soft shading are overall very pleasant, but I cant help but feel like the pose itself isn't as natural as it can be. Looking at references of people falling backwards their backs are all around much more reclines, and angle of the bend in the waist a bit more obtuse, so that may be worth looking into.
Also the simplification of the coat looks to lose continuity in the curve at the bottom swooping up, then coming back down and swooping back up again. The way the tails meet so far up makes it feel uneven in the distribution of fabric. There's exaggerating and taking liberties for effect, but you gotta look out for pushing it too far and becoming a distraction. Keep in mind the structure of a trenchcoat, the tails meet in the middle and are symmetrical, having such an intense discrepency needs to be justified with folds and further warping. My quick fix for this would be get rid of the second droop on the left, and just have it go straight from the fold under his but to the middle part.
Maybe drop the saturation on the jeans too, they're very blue, a little too blue for jeans in this minimalist style.
Also the top hand needs to be redone, hands are hard, but you really got the lower one done well, you are more than capable of a better hand than what you got right now. You got a reference attached to you, if you really need to, take a phot of your hand in that position at that angle and trace the shape in your art program. If you can take a shortcut take it, no shame in tracing your own hand, and no one needs to be any the wiser.
In general good, job on this one, the style looks nice, and there's some good textures, a bit more refining and you'll really get it going.