In the summer of 2019, Sega Online Japan created this summer time fun character art with a burlap and watercolor style texture. It features Sonic, Tails, Flicky, Cheese, Amy, Cream, Blaze, Silver & 3 other chao including a Sonic-type. They're all doing summer style activities and are drawn in a cute and almost classically styled way.

Sonic is shopping with a bag and holding a chili dog, the flicky is flying, tails has a pencil and is ready to draw, Amy is holding soft-serve ice cream and a baguette-bread (why?), Cream is bringing flowers to her friends, which has the Sonic-type chao smelling one while Cheese floats in the air holding a balloon. Blaze...just seems to be watching Cream. Silver has gathered apples in a bowl and is lifting one with his psychic power. He has shared the apples with one of the Neutral Chao, which has then split it and is sharing it with the other.
All of the Sega Online Japan items (all around on Gear) take this art, split it apart, and feature it to create many different things. The Online Campaign seems to be a web event where you send them 500 yen and something from the prize pool is then randomly dispensed to you in the mail. The pool has these post cards, keychains, pin buttons and also ribbon-handle shopping bags.
The post cards all have one full color side with 1 character (or chaos) chosen from the art work above, and one side with a solid color and line art logo. These are random-sold in the pairs you see above.