Gotta tell u, that for a first textureing, this looks amazeing! Well done! I once worked on a longbow modell (modified the very low poly-nodetail ingame modell of it), but could never texture it! Great work! I got some ideas how to improve, try to do some of them if you have time.
First, I would add a bump map. Even adding the original map u used works (seen the arrow I posted here, it has the same map for diffuse and bump), but thats a bad solution. If you made the texture useing an object/layer based software like PS, then I hope you still got the separate layers. The thing you should do is place the panel lines on a totally white layer, the image the same sized as your diffuse map of cours. Save it as anything, then ut it into the bump slot of the material. Next, add some specularity level to it, or the bump wont show. Leave glossines around 15. That should be a nice a metal.
Second thing you can do, is add "detail" to your diffuse map. add some fine dust, rust, scratches even.
I know an arrow shouldn't rust in space, but hey, that makes it look more "realistic" for the crowds
. You may also create a separate map for specularity level. That should be made from the new "dust layer", on a white sheet. This will make the light only gloss on the white places, so where theres no dust. Tip: convert the dust layer into something very dark grey. The specular map only uses grayscale value, so "color" doesn't matter there. BUT a nice rustbrown only onverts into something middle/light-gray. That would make the light gloos even there, just less. We don't want this, we want it Not to gloss at all!
It should also have the same pixel ratio as the original diffuse texture.
This is to ensure that every texture is in the same place without doing anything to them.
I'm not totally sure, but I think you don't need to have the same pixel-sized texture, jsut the ratio should be the same. Anyone know? Thanx.
So, I hope this will help a bit. If you'r really fed up with it though, I would be more than happy to practice dusting your texture for you
BTW, no point in turning a a texture into .jpg if you have the hard disk space to store larger formats. Why? cause before actuall rendering, the texture must be converted back into a the pixel based format.