the C4d looks like you just put it for the sake of having it, it looks decent but it could use some blending or something. does look nice still.
It looks way too sharp to me. The c4d's color seems to contrast too much with the rest too imo. Overall it's not bad though. Like the concept. Just tone down those sharp edges and it'll be cool.
The second one is better, but they both have a sort of low quality effect. They are good no doubt, but some low quality seems to be resting in there. Also, your text is tooo AA'd. It is one of the factors that show a bit of low quality, if you get me.
I agree with others - sigs are pretty nice, but the c4ds don't fit 100%, because of colour and contrast.. And the noise aroud the face is weird, like ang3l said. Maybe add some kind of border?