My favorite minis are Bitsy (mentioned above) and Penny's Worth. Both are registered at 1.5" blooms. Penny's Worth is registered at 10" tall and Bitsy at 18" tall, which seems about right from what I see in my garden.
Additionally, both rebloom consistently for me, meaning more blooms in the fall, so you get more days with their little faces showing.
If you are looking for something newer and fancier, you can do an advanced search on the AHS website, searching for blooms no greater than X inches. And then if you find something that strikes your eye, you can google "daylilies by [hybridizers name]" to see if they have a site they sell from. So maybe search blooms no bigger than 1.75" and registered no earlier than 2000?