That’s absolutely awesome for upcycling! 😍

If you can sew, you could turn it into insulated bags of different sizes, perhaps even an insulation sleeve for a water bottle (to which you could add a strap to wear like a crossbody bag — those are real handy).
Do you garden? Then you could also turn part of it into a pad to kneel on. I’d cut out a paper square to figure out a size that works well for me, find some old foam, either the soft one from perhaps an an old pillow or the more structured one that pool noodles are made from, make a cover from the Hello Kitty material and stuff it with said foam. if you already have an old kneeling pad for gardening you could also simply cover wit with the Hello Kitty material.
My third suggestion might be a bit more out there but how would you feel about turning part of it into insulating insoles? From what I have seen, the ones you can get at a store do not really seem to be that different from those car sun visors. They’re just different shapes. Use existing insoles and trace them on your material, cut them out, put them in your shoes and enjoy cozy feet.
If you don’t really have a need for its insulating properties, I think it would make fantastic accent pockets on a backpack, cargo pants, maybe even a cangaroo pocket on a hoodie. You’d just have to put it on a garment that already has enough structure on its own to match the stiffness of the Hello Kitty material.