To rice something must mean to customize and decorate. I'm guessing that it references the "rice rocket" term, originally a derogatory ethic slur. That term likely originated in the USA in the 70's or 80's, at first referring to Japanese motorcycles (which were fast, rightfully deserving the "rocket" designation: classic Japanese racing bikes are fully-fledged crotch rockets).

Sometime in the late 1990s, a Rice Rockets website appeared, making fun of people decorating their under-powered import econobox cars (not rockets in any sense) to look like racing cars with features like rear wings (on a front-wheel drive, lol), exhaust modifications ("fart cannons"), stripes, stickers, rims, steering wheels, etc.

If the cats decorating the desktop are Hello Kitty, she is really ricing it.