And here's an edit I did in addition to bollie's, I kept colors the same but tweaked the shading and some of the shapes to give him a more visible pose and a bit of depth.
Notably, I made the shading on that spiky anime hair a bit more uneven, to imply additional spikes facing the camera and better define the shapes on the right.
I also tweaked the shield to be at a more natural angle, most of the time shields are held at a slight angle unless they're held up Spartan-style right in front of the face (at least from what I've seen in movies), so I made it pitch at an angle. This made him look like he was taking a step forward/back, so I also changed his legs to give him a more guarded, sideways stance.
Fun fact: I actually took a bit of martial arts, and one of the basic things I remember from that long-ago time was that they do that sideways stance to reduce how much of you is available to the assailant to hit!
So, the more sideways a person is to the camera, the more a trained they'll look.
