Good starts. The first you just have to learn how to do Backgrounds the many ways you can, and get your render to flow with it or blend in. Right now she just sits on top of it. For the Morgan sig, if her render was lightened up a bit would make a big difference.
Just read up on tutorials and learn the basics that will become second nature later on. Keep at it, and I'm sure you'll do well in it. All it takes is motivation to keep trying

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I seriously need to do tutorials and practice, me sigs are the suxors compared to just about anyone around here =P.
But keep it up, and keep posting them =). Key to photoshop and any of these kinds of things is experience more then anything. You will always learn more, and it will always make you better.