The clipart is based on photographs taken at Rainbow's End on a Science / Physics trip. Those two were certainly having a lot of fun.
The wallpaper version is available at the preceding link.
Today's Gratitude Item: That the side mirrors in my car automatically fix themselves if they have been bumped back. Having mirrors get bumped back is one of the occupational hazards of parking at a school as kids tend to walk between parked cars without paying too much attention and sometimes they push the mirrors back as they go past.