I want to make you aware of a plugin I published right now: mediathumbnails.
Short description: Extracts a thumbnail from media files (ODT, DOCX, PPTX, etc.) in a media library and shows it on the wiki page.
I did some searches in the plugin repository, but as far as I can tell, this functionality has not yet been implemented. I hope someone can use this, and I'm glad for any feedback or constructive criticism!