A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
This texture looks like old leather. It should look great as a background on web pages.
Source V. Hartikainen
Prismatic Groovy Concentric Background No Black
Source GDJ
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
A light gray fabric pattern with faded vertical stripes.
Source V. Hartikainen
Abstract Ellipses Background Grayscale
Source GDJ
The texture of this background image has some similarities with leather, and it's colored in a dark brown color. So, if you are looking for a dark brown background image for your website, this may be an option for you.
Source V. Hartikainen