We have had a floor cushion / seat / footstool based on an alloy wheel with semi-slick tyre designed for us by Woouf (famed for their original and quirky soft furniture designs).
We call it the Mushelli. Size: is 56cm diam x 36 cm height. The design detail is excellent.
The Mushelli seat / beanbag / footstool is sold exclusively here – Mototile Mushelli Beanbag / Seat.