I took a picture last year that just seemed like it would fit well for an Ubuntu 16.04 wallpaper. My (now) wife made friends with a squirrel in Military Park, across from the Indiana State Museum. If you would like to download a full sized version, I have several links below.
Ubuntu 16.04 Wallpaper Downloads
I still retain copyright on these images. You are free to use them for wallpaper for no cost or attribution. However, you are not permitted to modify these images in any way without my permission. Go to the About Me page to contact me if you wish.