Four kobolds, stacked perilously on top of one another beneath a flowing robe covered in menacing runes. I'm sure everything will be fine. You should start running anyways though.

Everything from all the previous tiers. And also everything I published for 5e, for good measure.

You also get your name in the credits in the Four Kobolds in an Ominous Robe 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.)