Hoppers are, for the most part that I am aware of, considered to be a special case by the users and there has been speculation that they may become breedable in the future. This is primariy due to how different they are from the standard Kami - they have different colors and they started at lvl 1 and not 50 as most Kami do. It's possible this is an oversight or perhaps their exclusion for such a long time is confirmation that more is planned for them.
Carpo, on the other hand, is likely due to one of two reasons. A) There were a lot of fixes going on during Carpo's event and it's possible that the staff just hasn't gotten around to adding her picture to the Kami list yet, or B) Carpo is known to be part of the Seasonal Triad so perhaps all of their images will be added at the same time once they have all been released.
In any case I think this thread would be better placed under Help. True, a question for assistance isn't being directly asked, but at the same time it doesn't quite fit into the more conversation-based General Chat.