At the NASA web site is a story about how the first images returned from Mariner 4 were rendered by hand.
Do these images still exist, for example in a museum?
It was displayed publicly yesterday! At a Karman lecture held by Mr. Blaine Baggett, Director, Office of Communication and Education, JPL. It might not be archived and available to download right now, but soon it will. And I'm sorry for being a spoiler, but it is in the last few minutes of his show. Even the crayons used to draw it are preserved.
(I might add that I have no idea how this looks like anything on Mars. Does anyone know what region this could be?)
EDIT addition: Was this really the best map of Mars 50 years ago? According to the link TidalWave provided in the a comment below. With the old canali and everything. Some progress in space exploration has been made indeed. Methink I see triagonal structures on the early images from Pluto, but they might be like Lowell's imaginations.