When preparing an MCVE/SSCCE that involves images, it is useful to have direct access to images.
The types of images that would cover most questions are - small images in multiple colors or shapes, animated GIFs with/without transparency, JPEGs that are 'pairs' of pictures & can be used in image transitions, tile sets, sprite sheets..
Are there any small (under 30KB), on-site, license & royalty free images we can hot-link to for these types of examples?
Here are some example images for common use, mostly from existing answers on SO.
Simple Geometric shapes generated using Java as originally seen in this answer. It includes a Java based interface that defines the URLs and makes them easy to access.
Details: 32x32 pixel PNG (4 colors x 5 shapes) with partial transparency (along the edges).
Chess Pieces as originally seen on this answer that includes 2 other sprite sets (same image in different colors).
Details: 384x128 px (each sprite 64x64 px) PNG with partial transparency.
GIF is the only image format that supports animation. Here are a few examples.
Animated dashed border as seen in this answer.
Details: 100x30 px with filled BG (no transparency)
Zooming stars as seen in this answer, originally developed as a 'screen-shot' of a screensaver.
Details: 160x120 px with filled BG (no transparency)
Details: 60x60 px with filled BG (no transparency)
Orbital animation, originally developed for 1.1C. The orbits of the 'inner' planets (from Mercury to Jupiter, with an extra orbit shown in the thick of the asteroid belt). Better on a dark BG.
Details: 450x450 & 150x150 px animated GIFs with transparency.
Sunrise & moonset over the CBD of Sydney, Australia
Sunset & Venus over a telescope on Mt Stromlo, near Canberra, Australia.
Details: 480x320 px JPEGs x 4. (Displayed here at 1/2 size.)
Panorama at Dawn across the South-Eastern Suburbs of Sydney.
Details: 1474x436 px JPEG.
This Mercator map of Earth can be tiled left/right. Originally seen on this answer. The answer also includes a second version of the image that shows a semi-transparent line for the equator (which is not in the center, but significantly below it).
Details: 640x316 px (add 44 px at bottom to center equator) PNG with transparent BG.
For getting the URLs of the images, you might 'context click' on the image as seen in the browser and either: