How to make a real person in a game?

My brother wants me to put him in one of the games that I am making. I took a few pictures of him and I have a texture for a character that’s already in the game, just I can’t figure out how to make it look like the character is my brother. I’m using Gimp to do this. The texture that I’m trying to edit is below:

Texture

It seems like you could do that without too much trouble with blender. But I would suggest starting over with 123d catch (Versa Connector (TNDCI DEV) 0.0.1 - Sign On). That’s what I’m using for my game, though it’s very hard for someone to hold still long enough to take enough pictures to get it to look right.