Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
This seamless background image should look nice on websites. It has a dark blue gray texture with vertical stripes, it tiles seamlessly and, like all of the background images here, it's free. So, if you like it, take it!
Source V. Hartikainen
Retro Circles Background 5 No Black
Source GDJ
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer
A yellow tiled background... Blurriness, bokeh effect and rectangles pattern in one mix.
Source V. Hartikainen
Dark blue concrete wall with some small dust spots.
Source Atle Mo
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
With a name this awesome, how can I go wrong?
Source Nikolay Boltachev
Abstract Geometric Monochrome Pattern Prismatic No Background
Source GDJ
To get the tile this is made up from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The image a seamless pattern derived from a weed which I can't identify.The original weed image is from here:https://jp.pinterest.com/pin/500744052301423641/
Source Yamachem
A seamless background tile of aged paper with shabby look.
Source V. Hartikainen
A seamless pattern with wide vertical stripes colored in pale yellow.
Source V. Hartikainen
A seamless texture traced from an image on opengameart.org shared by Scouser.
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
Formed from decorative divider 184 in paint.net. Vectorised with Vector Magic.
Source Firkin
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
Prismatic Groovy Concentric Background 2
Source GDJ
Super detailed 16×16 tile that forms a beautiful pattern of straws.
Source Pavel
The tile this fill pattern is based on can be had by using shift+alt+i on the rectangle.
Source Firkin
Remixed from a drawing that was uploaded to Pixabay by DavidZydd
Source Firkin