Using SVG for background patterns is great because they are very small, vector, thus crisp at any screen resolution. So here are some useful tools to make SVG patterns for your website and download it.
Plain Pattern
Plain Pattern is an SVG based seamless pattern maker.
Delaunay triangle pattern maker
This project allows you to create beautiful high quality images featuring a nice pattern created from Delaunay triangulation and applying a flat surface shader.
SVG Patterns Gallery
This is a collection of svg-based pattern fills that can be used both as SVG patterns defs and CSS background image urls.
Patternbolt
Patternbolt is a fine selection of SVG pattern background, packed in a single CSS or SCSS file.
Pattern generator
Pattern generator based on the idea of the book forms of colors.
Trianglify
SVgeneration
Generate and download SVG images to use in CSS backgrounds for html and graphic design.
GeoPattern
Generate beautiful tiling SVG patterns from a string. The string is converted into a SHA and a color and pattern are determined based on the values in the hash. The color is determined by shifting the hue and saturation from a default (or passed in) base color.