OK, well this will probably end up being the wackiest of all the ideas you get, but in figure if its such a tiny space, why not have fun with it and be a little outrageous. So, toilet at one end, pedestal sink (or closed vanity at other end if you need storage), door in middle I presume - then wallpaper the whole wall with goldfish wallpaper. Paint ceiling a light green (if it's paintable). Do something that will make you and everyone smile the whole time they're in this room. They won't even notice it's small!