"Polished Stone", Gray Background Pattern #1053
Stone CC BY-SA 3.0A seamless gray background texture suitable for use on websites. To me, it has the look of stone. Feel free to modify it to meet your needs (by making it a bit lighter or darker, for example).
Source V. Hartikainen
More Textures
Diamond pattern 2 (colour 5) #2264
Blue CC 0From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background 4 No Black #463
Noise CC 0Prismatic Groovy Concentric Background 4 No Black
Source GDJ
Exclusive Paper@2X #24
Light CC BY-SA 3.0Paper pattern with small dust particles and 45-degree strokes.
Source Atle Mo
Skin Side Up@2X #848
Light CC BY-SA 3.0White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
"Animal Tracks", Background Pattern #1225
Yellow CC BY-SA 3.0A seamless pale yellow paper background with a pattern of animal tracks.
Source V. Hartikainen
Background pattern 314 (colour 2) #1838
Green CC 0The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
White Wave@2X #682
Stripes CC BY-SA 3.0Light and tiny, just the way you like it.
Source Rohit Arun Rao
Fall Leaves #243
Fabric CC 0Colored maple leaves scattered on a surface. This is tileable, so it can be used as a background or wallpaper.
Source Eady
Dark Wall@2X #818
Dark CC BY-SA 3.0Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
Dark Brick Wall #135
Wall CC BY-SA 3.0Black brick wall pattern. Brick your site up!
Source Alex Parker
Diamond pattern 2 (colour 6) #2261
Colorful CC 0From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Brick Wall@2X #1147
Wall CC BY-SA 3.0One more brick pattern. A bit more depth to this one.
Source Benjamin Ward
A dark wool background pattern with diagonal stripes #907
Stripes CC BY-SA 3.0Feel free to download and use it, or see the rest of the dark background patterns that I have made. Anyway, I hope you will find something that you like.
Source V. Hartikainen
Fabric pattern (colour 2) #2401
Fabric CC 0Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Black Mamba #57
Dark CC BY-SA 3.0The name alone is awesome, but so is this sweet dark pattern.
Source Federica Pelzel
Light Gray Fabric Pattern With Faded Stripes #965
Stripes CC BY-SA 3.0A light gray fabric pattern with faded vertical stripes.
Source V. Hartikainen
Well #1261
Wall CC 0Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Seamless Green Curtain Background #1333
Green CC BY-SA 3.0A free seamless background image with abstract texture of green "curtain".
Source V. Hartikainen
Diagonal Waves #1006
Gray CC BY-SA 3.0It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
Exclusive Paper #23
Light CC BY-SA 3.0Paper pattern with small dust particles and 45-degree strokes.
Source Atle Mo
Cream Paper@2X #1017
Paper CC BY-SA 3.0Submitted in a cream color, but you know how I like it.
Source Devin Holmes
Green and Yellow Lines on White Background #1000
Stripes CC BY-SA 3.0A seamless pattern with green and yellow diagonal lines on top of a white dotted background.
Source V. Hartikainen