First, let me say that these iphone backgrounds are gorgeous (I've posted about these before) but check out poolga.com if you haven't already.
Per usual, I'm getting around to changing my desktop background for the next month's calendar just before months end. If you're looking for a fun October wallpaper, go here and peruse. Lots of spooky options, so most are definitely seasonal. Having a halloween gathering? Get one of these spooky beauties up on your screen for a little decor ambiance.
Wallpapers come without the calendars as well. Nice for the person who doesn't update very often.