Flying Monkey - Angel wings and a tail. Face painting would help a lot here, if you offer it. Lion - Make a helmet with long brown braids and a red bow joining them at the top. A little face painting would make it toooo cute. A helmet with a point sticking up for the funnel.
Wrap curlicues around the arms and legs.
Draw on a scowling face. You can make a generic girl, then put a mouse-sized dog in her arms and call it Dorothy. I think you're much better off going for costumes than trying to create the lead characters from the film. Good pictures of Marvin, Royal and Patty, too.