Yea the main problem is that the render is lq.
You said that you did it yourself somewhere in the making-process.
If I where you I would search for that layer wich made the sig lq. Cause I think it's some sort of filter or something. Maybe you can still remove it cause it's kinda ruïning the sig imo.

I like the feeling of this tag tho.... the colors go well withc eachoter and the BG goes well with the render. I don't really like the effects at the left top corner of the sig.

The blending needs a bit work here. Espacially at the left side of the render. (left side for the viewer). Maybe some effect c4d's or some smuding would do the trick?
The text looks nice imo. Also you've created a pretty nice depht.. although I think the BG is a little bit overblurred.

Good Job mate.
Keep it up