Picked up a half dozen of these at my LFS today, from that experience and what I've seen on the net, it seems like the current pictures representing this particular species are not in fact Inpaichthys kerri, but Nematobrychon palmeri. Noticeable differences between the species are the presence of an adipose fin on I. kerri and the trident tail on male specimens of N. palmeri. Inpaichthys kerri is also much smaller than Nematobrychon palmeri, Growing to a max of ~1.5 in.
All of these photos are indeed the Emperor Tetra, aka Nematobrycon palmeri. None of these pics are Inpaichthys kerri. I love these guys and often call them the Tsar of tetras. I believe them to be some of the most beautiful of our freshwater fish. I would recommend them but in no less than a 20 gallon long--they can get rough on each other.