Deviantart, Interfacelift are great, and Abduzeedo and Smashing Mag both have some excellent high res Wallpaper round-ups.
I like to take mine out for a candle-light dinner, followed by a walk on the beach and a night of sensual massage.
you might try alta vista because their image search allows you to define an image resolution, and you can just select your screen res and search for general things you would like for your wallpaper.