The pose you chose for this soldier is quite appropriate and well chosen for a vertical portrait, and the background is perfectly done and toned.
The design looks somewhat similar to well known fiction figures, but you managed to add your own touch of ideas and deviation. It is a little sketchy and resembles the style of speedpaintings and concept design, but nonetheless it is able to deliver the soldier concept into the viewer's mind.
The colors are uniform in the image, everything neatly brushed, nothing awkward or eye hurting popping in any corner. I like that, makes it easy for me to stare at this for quite some time without getting distracted or disturbed.
Some more little refining might have helped deliver a better version, but you did a good job by adjusting the sharpness to an adorable degree.