[header] How to organize a' 70s carnival as a school fundraiser [title] Think about decorations. [step] Yeah, it sounds weird, but if there are not decorations your carnival will become epic fail for sure. Decorations create a special atmosphere which let all people feel that 70-s. talking about 70's, your possibilities are endless. 
It is a cute idea to use a lot of posters of movies that were super-popular in 70's. You can use pictures of actresses and actors, too.