I'm sure there is, but it's actually pretty easy, when you go to apply your C4D...open it up...convert to smart object, resize down to where you think it will be the correct size for your sig, then take the marque tool and outline only as much as you need to get all of the C4D, then click ctrl-c, to copy...then go back to your background and click
ctrl-v, to paste into your sig, then move wherever you want it, then pretty much have fun editing, etc. thank me if I helped lol :P