Ok I'll put it in points to save reading time.

1. The render looks extremely LQ. And badly cut for that matter too. Find more render sites or use the ones I gave you above, they are great for HQ.

2. Effect wise, I don't see much happening. It may be there but nobody can see it. Play around with the C4D settings more, perhaps try some smudging. For example paint down a color, smudge it then maybe liquify it too. Anything to make it stand out. Your C4Ds seem to be put on a black background on overlay or something, which will get you nowhere. Try Linear dodge, hue, linear light, screen, lighten. Vary it, develop new techniques perhaps.

3. The text. I highly suggest you read papas text tutorial. The link is here:
http://www.gfxvoid.com/forums/showthread.php?t=45209
Work on your placement and coloring. Grey stands out more then the render does and also if you're gonna do an entire line of text, pressing enter for a new line is the WRONG route to go. Make a new layer so you can put it closer, instead of spacing it out across the signature. Also the coloring. The signature tutorial by Papa will help you alot with this. Also if you want an easy thing to do is set it to white, maybe put on overlay, and lower the opacity. Over time you'll learn it but you gotta work on it.

5. Color palette. The final critique. Basically, black doesn't compliment the renders colors of cream/brown/green. Neither does grey. Find a color scheme that works with the sig, that makes it fit in and not distract you or make something stand out too much. At the moment it makes every aspect stand out and you have no idea where to look, especially with the random 2 white dots on either side of his head. Every sig needs a color scheme.

Red on green is a no, just so you know..