A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
This is a seamless pattern of regular hexagon which has a honeycomb structure.
Source Yamachem
A repeating background with wood/straw like texture.
Source V. Hartikainen
You just can’t get enough of the fabric patterns, so here is one more for your collection.
Source Krisp Designs
Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
A new one called white wall, not by me this time.
Source Yuji Honzawa
Like the name says, light and gray, with some small dots and circles.
Source Brenda Lay
The image depicts a seamless pattern of pine tree leaves.
Source Yamachem
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A large (588x375px) sand-colored pattern for your ever-growing collection. Shrink at will.
Source Alex Tapein
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Prismatic Floral Background No Black
Source GDJ
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
The image depicts a seamless pattern of Japanese Edo pattern called "kikkou-matsu" or "亀甲松" meaning " tortoiseshell-pinetree".The real pinetree is like this: https://jp.pinterest.com/pin/500744052301065077/
Source Yamachem
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton