Do you expect an internal image editor in LibreOffice such as Microsoft Office's one? Do you want to crop, annotate, adding text, and so on to images in your document? Unfortunately, it is currently impossible. But I found a single trick to do advanced image editing easily from the outside of LibreOffice. The main tool to do this is LibreOffice right-click menu, Edit with External Tool. Then you just need Gwenview and Shutter to complete that. Currently I am writing a book about Linux and this trick helps me so much.  I use it almost in every page in my book. For certain people, maybe this tutorial looks like a mess at the first glance. But trust me, if you use it for long term usage (like me, writing a book), you will find no other way easier than this. Of course until LibreOffice finally has internal advanced image editor someday.

Shutter as External Image Editor for LibreOffice