Online repositories of scanning electron microscope photographs?
First off I'd like to reccomend the University of Dartmouth's publicly available collection located here.  They have both SEM and TEM images of a wide range of organisms and cells from algae to see urchins through everything from cholera to mammalian cells.  Images are high quality, fully captioned and properly attributed.

I'm a little confused as to the problem you're having with google - see my original comment on your question.  However I have looked at the photos of Wikimedia Commons in the SEM category and see that they are either images taken with, images of SEM Microscopes or technical drawings regarding their function.  I assume that you're looking for the images taken with SEM.

I was able to find a great number of similar images to those in the commons with a Google Image search - I read above that you were having problems with this approach so perhaps try the search term "SEM images" in image search (or this search to avoid duplications from images you have already seen on Wiki Commons)?

Examples found on just the first page: