Nintendo recently updated its character profile and Mario Kart history pages on the Japanese Super Mario portal website. Unfortunately these new descriptions are currently only available in Japanese, but it's easy to enjoy the artwork and design.
In a neat touch you can listen to character sound effects in their bios, as well as see a bit of artwork. The Mario Kart history page also looks fantastic.
Of course, Mario Kart 8 Deluxe is just around the corner, so there's plenty of excitement and nostalgia around the franchise at present.