oops, didnt see your post.... doh
Ok, the biggest thing that sticks out, is it look real new. Also, maybe alittle complex, but still... you just need to add some 'dirt' texture to it.
If you head over to
www.gurusnetwork.com , in there PS section they have a good tutorial by DarkGarden on 'weathered metal'. I think that would really help you get an older used look to your shield.
You have to remember that this stuff usually is not learnt overnight, it takes some time experiemtning with various tools and techniques to get better. Just stick with it and keep practicing. Thats the key.
A quick trick that might help is to create a layer above your shield, do a render-clouds (default colours), change the layer mode to colour burn, lower the opacity and do some gaussian blurring to make it look less like clouds...
or try a new layer, fill with mid gray, change the layer mode to overlay and go to work on that layer with the dodge/burn tools and some scratchy brushes....
