Way back in 2014 I also asked that question and it seemed to be that you'd need to edit how promos work to be able to do things like have custom names, seeing as promos are handled by making the code in the promocode part of the admincp as well as designating what adopts belong to that code.
So IntoRain helped me with how to add a custom adopt from an image instead. That way you can control what species, the image used, the name, all the DB data. I remember it working pretty well back then so it should work now
Here you go:
http://www.mysidiaadoptables.com/for...m+adopt&page=2
It's a little more involved in the sense you make custom pages for the adopts, but it's definitely the most customisable option