Background pattern 215 #2371
Brown CC 0A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
More Textures
Subtle Carbon@2X #950
Dark CC BY-SA 3.0There are many carbon patterns, but this one is tiny.
Source Designova
Seamless Wood Pattern #889
Wood CC BY-SA 3.0A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.
Source V. Hartikainen
Background pattern 314 #1839
Yellow CC 0The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Background pattern 313 #1858
Dark CC 0Background pattern originally a PNG drawn in Paint.net
Source Firkin
Diminishing design 5 #1725
Blue CC 0Adapted from an image that was uploaded to Pixabay by Anerma.
Source Firkin
"Glossy Pink Fur", Pink Background Pattern #1235
Pink CC BY-SA 3.0Here's a quite bright pink background pattern for use on websites. It doesn't look like a real fur, but it definitely resembles one.
Source V. Hartikainen
Prismatic Geometric Tessellation Pattern 4 No Background #557
Noise CC 0Prismatic Geometric Tessellation Pattern 4 No Background
Source GDJ
Concrete Wall 2@2X #80
Wall CC BY-SA 3.0A light gray wall or floor (you decide) of concrete.
Source Atle Mo
Pinstriped Suit@2X #666
Dark CC BY-SA 3.0Just like your old suit, all striped and smooth.
Source Alex Berkowitz
Background pattern 18 #202
Dark CC 0A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
Prismatic Snowflakes Pattern No Background #411
Light CC 0Prismatic Snowflakes Pattern No Background
Source GDJ