A seamless pattern based on a tile that can be achieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857
Source Firkin
A yellow tiled background... Blurriness, bokeh effect and rectangles pattern in one mix.
Source V. Hartikainen
Abstract Ellipses Background Grayscale
Source GDJ
A seamless pattern with wide vertical stripes colored in pale yellow.
Source V. Hartikainen
Can never have too many knitting patterns, especially as nice as this.
Source Victoria Spahn
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Seamless Olive Green Web Background Image
Source V. Hartikainen
A textured blue background pattern with vertical stripes.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 2 No Background
Source GDJ
Same classic 45-degree pattern, dark version.
Source Luke McDonald
Here's an yet another background for websites, with a seamless texture of wood planks this time.
Source V. Hartikainen
A white version of the very popular linen pattern.
Source Ant Ekşiler
Remixed from a raster on Pixabay that was uploaded by ArtsyBee.
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
You just can’t get enough of the fabric patterns, so here is one more for your collection.
Source Krisp Designs
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
It was called Navy Blue, but I made it dark. You know, the way I like it.
Source Ethan Hamilton
Floral patterns might not be the hottest thing right now, but you never know when you need it!
Source Lauren
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
A free background image with a seamless texture of cardboard. This texture of cardboard looks quite realistic, especially when is actually tiled.
Source V. Hartikainen
Used in small doses, this could be a nice subtle pattern. Used on a large surface, it’s dirty!
Source Paul Reulat
It’s an egg, in the form of a pattern. This really is 2012.
Source Paul Phönixweiß
The image depicts a Japanese Edo pattern called "kanoko or 鹿の子" meaning "fawn" which has a fur with small white spots.
Source Yamachem