Did you embed the images or were they linked? If they were linked from some file on your computer, then of course they wouldn't see those particular images. For images to be seen they can't be linked unless on a server online, but must be embedded. Libre Office allows you to save files in various formats, including windows formats. This sounds more like an error by you in how you created the documents.
Just spent all afternoon doing a quiz on Libra Office, sent it to my boss as a RTF file but when on opening have discovered it's converted it to a spread sheet and also deleting some pictures I also had on there.
Have sent the files after a panic in ODT files, but I'm worried he won't be able to open them which will be a pain as have spent hours typing away. How do I prevent this from happening again?