I had this on the Paradox Forums, but just thought to look to see if TWC had a board for it, which it did.
What I said there:
"This is my step-by-step walkthrough on putting new emblems into the game's nation designer, as I've yet to see someone do a tutorial on it. It took me for-bloody-ever to figure out how to do this, so I thought I would spare others the trouble."
https://www.youtube.com/watch?v=iWi8SeIh-as

And now that, post the 1.15 update, Paradox seems to have added new emblems themselves, changing the structure of the file, I've created a supplement to compensate. Thus, here's part two of the tutorial:
https://www.youtube.com/watch?v=s79P78Wt1do