I always use one of my picture. I used to put a calender on it as well but have stopped doing this last year. I used to send these to friends every month. I guess after never hearing back from them I thought most were not interested or didn't want to have the trouble of changing their desktop pictures.
So here's mine that there now. As soon as the first snow is here, I'll get another one. I've posted this pic before on my daily 365 whatever.
It's a shot taken of a window from the local greenhouse.