As slow as possible

  Jurassic Park Theme (1000% Slower) by birdfeeder

Blue spheres

AquaGems. The patterns visible in some are reflections from the glass container.

"Fried" marbles, with internal fractures caused by rapid heating and cooling

Mandelbrot variations

Mandelbrot Pearls

Nebulabrot

Source for both images.

"Illustrations of Madness... Embellished with a Curious Plate"

Illustration of the "air loom" imagined by 18th-century paranoiac James Tilly Matthews, who believed that such a device was being used to torture him from a distance.

The full title of the 1810 book which contains this image is: Illustrations of Madness: Exhibiting a Singular Case of Insanity, And a No Less Remarkable Difference in Medical Opinions: Developing the Nature of An Assailment, And the Manner of Working Events; with a Description of Tortures Experienced by Bomb-Bursting, Lobster-Cracking and Lengthening the Brain. Embellished with a Curious Plate.

The poet's mistress

The ideal of feminine beauty in the 17th century demanded that women have the characteristics that are literally depicted in this illustration from Charles Sorel's The Extravagant Sheperd (London, 1654): teeth like pearls, eyes that sparkle like the sun, eyebrows arched like Cupid's bow, cheeks a-bloom with roses, and breasts like little globes or, as one writer put it, "little worlds of beauty."

A colored version can be found here.