I was very impressed with this: http://i342.photobucket.com/albums/o.../cokesotw2.png
You should try more signatures like this.
As for your other signatures, I see that you're still using a lot of effect C4Ds along with solid C4Ds. That's okay, but it seems like a lot is lost through this and makes little room for negative space. Try creating a bit of depth by simply sharpening what's in front and blurring the background.
I have a little challenge for you. Try making a tag only using brushes (the default Photoshop brushes) and the pentool.