That looks really good for a start. Some tips i think work well while ive been making my TF2 textures.
The cutout filter works wonders if used correctly, even valve has used it in some of their textures. Id run the filter across the paint stripes you have, it helps simplify the range of shades. I cant really tell from the shot (dont think you really have any in the texture,) but try to keep as little direct shadowing in the texture as possible (even less than you normally would.) In most cases keep highlights but try to use a pale warm colour. I also found a hard edged brush with a low opacity works best, hand paint as much as possible and dont worry about small mistakes, they help add to the character. Finally i flattened my textures and duplicated the base, i ran the cutout filter across this and then set it's opacity between 20-50, it helps add some blocks of colour, hide any messy painting and tie together sharp changes. Finally, make use of normal maps and detail maps, specular isn't used too much compared to other games.