Unreleased Karts (2017)
On Dribble.com Chris Bishop made a post about new karts are going to released. They were released in 2018. But, they could also be secret codes we don't know yet. The teal square depicts, whom we now know as, Pinewood, the new character that was coming to Kart Kingdom. A lot of users were happy about the new characters and possible items being added.
On July 1, 2017 and as well as September 11, 2017, images of them were found in the game files by a couple users. Other unreleased karts were found too.
This image was later revealed to be promo art for Kart Kingdom Racing. Most of these items are probably for the characters in Kart Kingdom racing only. It is possible that the items will never be released for public use, however developer accounts probably have them.