When you are writing your book in plain text on Leanpub, you may find that the way floating images and text work together is not always working perfectly. In fact, sometimes it doesn't really work at all. This is something we may address in Markua at some point.
Our general policy at Leanpub r.e. floating images is that they aren't really all that well-suited to ebooks that are produced in multiple formats from a single source manuscript, and that are going to be read on a variety of devices, where people can change fonts and font sizes.
We have an InDesign export option for making books look super nice once an author is done writing their book, and we have a "Bring Your Own Book" mode people can use to upload super-nicely formatted files for sale on Leanpub.
If you really want to curate your book with floating images, you can use a little hack to insert blank lines that can clean things up a bit. You can create blank lines by essentially adding single cell tables, by putting two pipes with a space between them | | on a line by themselves.
If you do this:
In between paragraphs and images etc., you might be able to get the floating images to work better.
However, to repeat, our best advice about floating images and wrapping text is to just save your time and not do it :)
Floating images occasionally do work nicely, but more often than not they leave something to be desired. If you are in our help center, chances are this is one of those times!
Basically, it really only works decently for small images (about the size, say, of the circle face in your image), and not in conjunction with anything but normal paragraphs.
Our PDF rendering is done with LaTeX, which is great, but it's really old and it's not good at the types of layouts you see in magazines. It is, however, good at the types of minimalist layouts you see in books :)
Finally, for the people who read your book in EPUB on a phone, they will not care about, or benefit from, any work spent floating images.