I wrote one such piece -- "Whichever Path You Choose" -- as part of Writer2Writer.com's Photo Contest #2 (2003). The idea was to write an opening paragraph based on the photo shown below. My entry won first prize, but I could never manage to build on the opening.
In hopes of kick starting the creative process, I've decided to post the opening here:
I peered inside both tunnels, straining to detect any sign of movement within a dozen shades of grey. Jane's breath felt humid against the side of my neck. Her nails dug deep into my upper arm. All I noticed was the pressure. Pain would have to wait until the general numbness passed--maybe in a day or two. I grabbed her clutched hand and whispered, "Do you think he's really dead this time?"
She wrapped her arms around me and nuzzled my shoulder blade. "We can only hope."