How can I make the background of this fit in with Sythe?

Heres the pic:

 

You can use the eye dropper tool to get the color from one of your posts

then in photoshop use the magic wand tool to select the backaround and fill it will the color you use got from the eye dropper.

 

Hm.. Sounds good..
How would I round the edges (corners) of the picture?

 

Assuming you made the file in photoshop, just delete the background layer (if there is one) so it's on a transparent background, and save the file as a .png.

Not exactly sure what you mean. If you wanted the sig in the shape of an oval, for example, simply use the oval selection tool, select and delete the inverse of that, and save the file as a .png.

 

Fail... Dont worry about it. Thanks guys. <3

 

Assuming that this is done.. Right.
If not; Get the person that made it to delete the background in Cinema4D, save it as a .png and you're ready to go!
Closed as problem is most likely solved.