If you are into designing for multiple resolutions, SVG is the best option to turn to as far as the use of graphics is concerned. SVG Loaders is a collection of simple SVG loaders and spinners created and released by Sam.
You can make loading icons and small animations built purely in SVG, no CSS or JS. All SVG files are fairly small in size, but you can make them even smaller by minifying with something like SVGO.
Website and Demo: http://samherbert.net/svg-loaders/
Download: https://github.com/SamHerbert/SVG-Loaders
License: MIT License