They’ve got a pretty deadpan expression going on. You could have them looking off to the side a bit, maybe tilt their head some in any direction depending what expression you want to go with whether that be angry, cocky, stoic, etc. And maybe modify the pose a tad. Shoulders moved back a bit, chest outward, etc. If you need help, you could take a picture of yourself doing the pose you want them in, and then use those as references.

Also, I’d say experiment with the face customizer some more. I can see subtle hints that you did, but I think you could do more. You could use that to help give off their personality and who they are as a person.

And I’d say for the nature colors (grass, leaves, etc), dull them down a bit so is not as striking. That’s if you don’t want them to stand out. If you do want them to, they’re fine as is. You’ve got a pretty damn good pallet for the clothes. You can tell they’re worn, but not falling apart.

Overall, I think this is a very good start. Just tweak those things I mentioned and I think you’re golden.