Using published images from scientific papers in blog posts

Pedro did some digging to figure out what are various journals’ policies regarding use of images – figures from the papers – in blog posts. It is all very vague and most journals do not have anything specifically targeting online republication, but the Fair Use rules should apply.
I have often used images from papers in my posts, usually only one, sometimes two from a single paper, which should be OK under the Fair Use system. In some cases I used figures that are many decades old, reprinted in every book and textbook in the field, used in every chronobiology college course in the world, and seen many times on slides at conference talks. Such images are now informally considered a common property – they are the icons of the field.
I have used more than 1-2 figures from a paper ONLY when I wrote posts about my own papers. But I do have the originals so I can always claim the ownership, or at least state that they were “redrawn after” an image in the paper (who cares what is redrawn after what and which image chronologically came first?).
Anyway, what do you do? Do you use sites like Free Biomedical Images?