I think it’s adorable. If you can make it work functionally for you, I don’t see a problem With aiming for something esthetically pleasing.  It will get covered in dust and poop, and they may peck at the wallpaper, but if you go into the build knowing that, you can modify yours accordingly 

 I would aim for a different color other than red, bc I don’t like it, and I wonder if the wallpaper being red attracts pecking more.  Also add a dust bucket if you’re going to do the gravel flooring.  I’d actually do construction sand in the run instead.  I love that fountain tho!  I bet the girls would love that.  Hard to keep clean, sure, but maybe provide another source of water in a regular waterer for them, too.