The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
This background has abstract texture with some similarities to wood.
Source V. Hartikainen
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
A pattern formed from a photograph of a 16th century ceramic tile.
Source Firkin
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
A free pink background pattern.
Source V. Hartikainen
A free light orange brown wallpaper with vertical stripes designed for use as a tiled background on websites. An yet another background pattern with vertical stripes.
Source V. Hartikainen
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
A white version of the very popular linen pattern.
Source Ant Ekşiler
Prismatic Hypnotic Pattern No Background
Source GDJ