Patternico is a brilliant pattern-maker tool. Just put in the icons of your choice and edit as you like
Lost And Taken has an excellent selection of free textured stock photos.
Transparent Textures is a tool with hundreds of customizable CSS textures.
Toptal.com/Designers/SubtlePatterns has Lots of free patterns in PNG format.
CoolBackgrounds A tool for making header backgrounds. Very handy for social media headers.
TextureKing Very graphical textured photos. Gravel, concrete, rust…
HeroPatterns Seamless SVG patterns that will look great in web applications.