Placement of illustration: before/after text?
Figures always go after the first reference to that figure. 
Figures always have a caption. In almost all styles captions go after the figure, but before tables. 
Having a figure as the last thing in a section looks a bit odd and you might want to stick in an extra sentence just so it doesn't look odd. Having said that- you can avoid this by not dividing the text very finely (that is, no sub-sub-sections).