This is a bit difficult for we average folk, but you might consider mummification, as the Egyptians did with their kings. I have no idea how you'd do this but try checking online. The Egyptians used a very specific technique, but bodies have been mummified through normal processes, like being buried in salt in a certain climate.
Perhaps a more available process is taxidermy. People who do that work preserve the body, remove internal organs and such, and replace them with some kind of substance to hold the body in place. A good one can do a very realistic job for you.