I think that doing a 2-Dimentional, stencil type, design or portrait on the black top of a basketball court would be a fun venture. The impermanence of snow would make for such a design to be a worthwhile venture, as they can be accomplished relatively quickly.
I also think that recreating a Calvin and Hobbes snowman scene would be terrific.
There is a park on Plumas St., where the hill slopes down before the fencing (leaving whatever is constructed in perfect view of the passing traffic, without obstruction), that could be perfect for such a venture. And there are hundreds of scenes to choose from, and a great amount of room for improvisation with this idea.