DeArrow is an new browser extension I just released for crowdsourcing better titles and thumbnails on YouTube. The goal is to make titles accurate and reduce sensationalism.
Titles can be any arbitrary text. Thumbnails are screenshots from specific timestamps in the video. These are user submitted and voted on. By default, if there are no submissions, it will format the original title to the user-specified format, and set a screenshot from a random timestamp as the thumbnail. This can be configured in the options to disable formatting, or show the original thumbnail by default.
It's still in beta right now, but should be ready to try out!