I decided to upload my wallpaper to WinCustomize.com. They accepted it! I was kinda doubtful since everything else on there seems to be entirely digital artwork, not originating as photographs, whereas mine is just the opposite. Plus, being a photo, it's not as "clean" as digital renderings at high resolutions. It was shot at 1600x1200, but noise is still visible even at 800x600.
Oh well. People are downloading it. Yay! :)
Here's a link to the wallpapers section of the site. Mine will slowly move down the list sorted by date updated, so you might need to search for it. The wallpaper name is "Impact".