Shorter answer, even if you hand edit CSS, the idea of images with text flowing is doomed. What Wordprocessors call page or paragraph anchors and what a web page calls Float Right or Float Left.
Even on a web page it's unpredictable, I have to put a HTML special break so inappropriate text from a next paragraph heading doesn't end up beside the image if the user uses small text. Possibly <div style="clear: both;"></div>
Having a centred image with paragraph break before and after, optionally with a width setting (never height) will work. A character anchor in Word or LO Writer. If you use a paragraph style to centre that will automatically become CSS.
It's reliable for paper and thus PDFs, which are either for 10
" or larger tablets or proofing paper. Because the user can't change the page size, font face/size or anything.