Ummm, I suggest that you work on the modeling more before you get to the UV-ing/texturing.
Not that the model is bad, it is good but you can work on the mouth area, define the shell boundaries, define the legs more... etc.
And if you choose to go ahead anyway- I don't like the texture for the body, if you have Photoshop I suggest that you take your UV layout, put it in Photoshop, and then get a ton of pictures of turtle shells and maybe warp them or paste, blend ETC onto the map.
That's what I can suggest, and- don't make the horns shiny and reflective, please, it makes the overall picture look bad.
Try to make them a diffuse yellow-ish or whatever color-ish color you want and make a bump map.
l8er,
Matt
Live the life you love, love the life you live