Okay, I held out all day to see if anyone else cared to hazard a guess at my game of guess-what. No dice. For items one and two, I have combined the solution:
Low-magnification view of a nail file resting on a mousepad.
The first item was the surface of a mousepad at high magnification. Weird stuff; the thing looks like black fabric, but lights up like spun metal when you hit it with some illumination*. Natural fibers do not do this. The second item was a close-up of the nail file in the foreground. The regular pattern was the ridges of the file; microscopy is not good at preserving depth cues. The whitish particles, then, are most likely fingernail dust, but I didn't investigate their composition.
The third photograph is the edge of a floppy disk, with the metal slip cover pushed back. While seemingly in good condition when viewed with the naked eye, under a microscope many small scratches are evident on the surface. I don't, off the top of my head, know whether the mottled texture of the disk corresponds to the grain size of the magnetic substrate, but it seems a bit large for that.
*Photomicroscopy takes a lot of light, after all. Think about it: by magnifying a scene, I'm greatly spreading out the light that originally struck it. At 10X, an object will appear about 100 times less brightly lit than to the naked eye. To take a photograph with any kind of reasonable shutter speed then requires an enormous amount of light, and comments were made that glancing at my objective stage was not unlike looking at the sun. Despite our very cool-running fiberoptic lights, I wound up melting the floppy disk (the actual disk, not the outer shell).
For comparison, taking a photo in full noonday sunlight with the pupil wide open calls for about 1/500 to 1/1000 second exposure time. With an optical zoom factor of around 15X my light source is diluted by a factor of 225, so the optimal exposure rises to 1/2 to 1/4 second. I haven't rigged up any stabilization, so that won't work. Meaning I have to use brighter-than-full-sunlight illumination.