Well, you have a decent grip on the basics, such as positioning. Not much other than the basics. None of your renders blend into the backgrounds at all.
The blur on the first one doesn't make it blend in better, and you should avoid doing that.
A method that I find makes blending easier is using an external source of light and a soft white brush to help the render and background blend.
Tone down on your C4Ds, they really don't help make signatures look better unless you are very experienced at their use and placement, and, seeing as you are new at it, I suggest you don't use any until you become better at the basics/intermediates.
Lighting effects(like the one in the 2nd siggy) should only be used when you fully understand how to use them. I have the particular one you used, and, you didn't use it to its full potential. They're referred to as lighting effects for a reason, and you're using it wrong.
Also, for your texts, use something sleeker, like trajan pro or neuropol.