I've spent a lot of time trying to find picture books to read on my ipad (via the Kindle app) and I can honestly say that I have really, really struggled to find any self-published picture books in e-book form that are top notch. Some are okay – the pictures are reasonable and the text is fine – but I just looked through my ipad to find some and realised that my daughter has deleted all of them, leaving only the traditionally published ones behind!
This company's books are basically self-published (ie they're published under the name Little Star, but the authors/illustrators ARE the publishing company) and they're pretty good, compared to what's out there: http://littlestarbooks.com/
But honestly, I'd love to find more high quality self-published stuff, it's just difficult to find among all the stuff that's been put together by people who aren't that great at illustrating or aren't that great at designing or aren't that great at writing or all three!
PS In terms of layout, one thing I dislike about some e-PBs is how the text is all on one side and the image on the other, although I understand that for e-books it can be useful if the text size can be increased/decreased. I just think picture books are a different beast and should be treated as such. In picture books the text is often PART of the illustration and that shouldn't change just because it's in e-book format, I don't think.
Hope that helps a bit!