Web Backgrounds and Seamless Textures
   http://www.ender-design.com/rg/backidx.html

Pattern Cooler designs
   https://www.patterncooler.com/

Background Sections
   http://www.backgroundsgiant.com/backindex.html

3Quarks Background Patterns
   http://www.3quarks.com/Backgrounds/index.html

Texture Backgrounds
   https://unsplash.com/backgrounds/art/texture

Texture Photos
   https://www.pexels.com/search/texture/

Pixabay Textures
   https://pixabay.com/images/search/texture/

Ava7 Patterns
   http://patterns.ava7.com/

Transparent Textures
   https://www.transparenttextures.com/

50+ Free Grey Seamless Patterns (colors) for Website Backgrounds
   https://www.designbolts.com/

Background Labs Backgrounds
   http://backgroundlabs.com/

Gradient Backgrounds
   https://bit.ly/2K36z5L

Super Dev Resources Seamless Patterns
   https://superdevresources.com/free-seamless-patterns/

Red, White, and Blue Backgrounds
   http://wallpapersafari.com/red-white-and-blue-backgrounds/

Subtle Patterns                           (recommended by Vosive)
   https://www.toptal.com/designers/subtlepatterns/

freepik                                       (recommended by Vosive)
   https://www.freepik.com/

Absolute Background Textures Archive   grsites
   http://www.grsites.com/textures/

Free Desktop Wallpapers       (web search)
   https://tinyurl.com/y8b794bp