The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Prismatic Groovy Concentric Background
Source GDJ
Adapted from an image that was uploaded to Pixabay by Anerma.
Source Firkin
This could be a hippy vintage wallpaper.
Source Tileable Patterns
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
You know I’m a sucker for these. Well-crafted paper pattern.
Source Mihaela Hinayon
From a drawing in 'Worsborough; its historical associations and rural attractions', Joseph Wilkinson, 1879.
Source Firkin
A very dark spotted twinkle pattern for your twinkle needs.
Source Badhon Ebrahim
A version without colours blended together to give a different look.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
A large (588x375px) sand-colored pattern for your ever-growing collection. Shrink at will.
Source Alex Tapein
A light background pattern with diagonal stripes. Here's a simple light striped background for you.
Source V. Hartikainen
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A rusty grunge background for websites. Feel free to use it in your site's theme.
Source V. Hartikainen
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady