USA Flag Has a very nice cloth/handmade feel to it, if that's what you were going for, then great job! You could however add some sort of constant shading with a main lightsource. Right now it is kind of flat with the exception of the detailed texturing. What it is missing is the overall lightning creating the illusion of it actually being a real object.
What I mean is this http://i1-linux.softpedia-static.com/screenshots/American-Flag-Theme_1.jpg - The best example I could find with a quick google search. If you pay attention to the lighting on that flag, you see it is brighter at center-right(the artist chose the center-right as the source/origin of light.). This adds another whole layer of depth and beauty to the picture. Try imagining it without the lightning, if you can. You should start to understand why that last touch is of such importance.
To emulate such lightning effects, you could either use manual work, manual editing(Dodge/burn tool in ps for an example), or for ease and quick quality results, the filter->render->lightning effects tool in PS. Mixing and experimenting with different ways is the best way to learn in the long run, you often have to mix different methods to achieve the effects you want at higher level editing.
Layer masks are also a great tool for these things, though it might be best to leave that for later when you understand the system better to begin with :).
