You send me an idea for a unique legendary kobold, and I turn it into a leader stat block for Draw Steel – complete with villain actions. Then you get to show it off to your friends and say "this was my idea". And if you’re lucky, your director tries to kill your party with them.

When I did this for 5e as part of my last crowdfunder, ideas included "wild west gunslinger", "information technology", and "Swedish Chef from the Muppets". So, you know, there's quite a range.

You also get the PDF and your name in the credits in the Three Kobolds in a Trench Coat backer section. 

(Depending on the number of backers with custom kobolds, these will either be in the Kobold Ancestry PDF, or a separate collection of stat blocks. If it's the latter, you'll get both PDFs as part of your pledge.)