After unpacking items stored inside the aircraft, found that the interior was a perfect mouse hotel. It appears that they have been in there for quite some time. Quick inspection shows that the mice have left droppings/urine in all areas of the aircraft, including under the floors at the feet, seat, and baggage areas. Unfortunately, these areas have panels that are riveted into place and may have to be pulled up to gain access to ensure thorough cleaning. An email has been sent to Van's asking if a 9:1 water/bleach solution would be OK to clean and disinfect without creating other issues such as corrosion. Also, need to thoroughly inspect wiring and plastic tubing (brake lines, pitot, static, etc.) to make sure that the little bas#!@$ didn't chew through any of them.