Satin Weave #1044
Light CC BY-SA 3.0Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
More Textures
Wavy background #2018
Colorful CC 0CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Fence 6 #2575
Wood CC 0A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Seamless Gray Stone Background #1028
Stone CC BY-SA 3.0This background image has seamless texture that resembles a surface of gray stone.
Source V. Hartikainen
Decorative divider 231 #2149
Dark CC 0From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
Diagonal Striped Brick@2X #680
Stripes CC BY-SA 3.0Might not be super subtle, but quite original in its form.
Source Alex Smith
Aged Paper Background Tile #1074
Paper CC BY-SA 3.0A seamless background tile of aged paper with shabby look.
Source V. Hartikainen
Subtle Surface@2X #926
Light CC BY-SA 3.0Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
Pink Clouds Background #1230
Pink CC BY-SA 3.0Actually, there's no clouds in it, but I think it looks quite nice.
Source V. Hartikainen
Decorative divider 211 #2362
Dark CC 0From a drawing in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
"Black Metal Grid", Seamless Background Pattern #1080
Metal CC BY-SA 3.0A free seamless background pattern for use on websites.
Source V. Hartikainen
Tex2res2@2X #720
Fabric CC BY-SA 3.0Number 2 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Background pattern 214 (colour 5) #2374
Green CC 0A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
Background Patterns - Cerulean #245
Fabric CC 0f you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Decorative divider 236 #2090
Dark CC 0From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
Decorative divider 229 #2151
Dark CC 0From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
Retro Intro@2X #894
Gray CC BY-SA 3.0A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
Tessellation 15 (colour) #2222
Blue CC 0The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin