The only things I see that is wrong with it is

1. The red seems a bit too bright, actually it seems all the colors needs to be darkened a bit and faded some

2. Theres no white outline on the gun mantlet or whatever its called

4. It doesnt fade in the back

5. The eagle doesnt have its mouth open

6. The star on the gun barrel is waaay too big.

Other than that its great. I suggest you take some time when you can and make a more redefined and detailed version that is waay closer to the actual one.