Wavy background #2021
Pink CC 0CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
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Fire diamond #2488
Diamond CC 0U.S.-based National Fire Protection Association standard fire diamond for flagging risks posed by hazardous materials. The red diamond has a number 0-4 depending on flammability. The blue diamond has a number 0-4 depending on health hazard. The yellow has a number 0-4 depending on reactivity. the white square has a special notice, e.g OX for oxidizer.
Source Firkin
Decorative divider 236 #2090
Dark CC 0From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
Spiral background 2 #2245
Colorful CC 0Remixed from a raster on Pixabay, that was uploaded by ArtsyBee.
Source Firkin
Fabric pattern 2 #2396
Fabric CC 0Not 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
Background pattern 245 (colour 2) #2191
Green CC 0This was formed by distorting an image of a background on Pixabay.
Source Firkin
Noisy #45
Paper CC BY-SA 3.0Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
Tessellation 16 (colour 4) #2212
Green CC 0The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Light Aluminum #304
Wall CC BY-SA 3.0Used correctly, this could be nice. Used in a bad way, all hell will break loose.
Source Atle Mo
Subtle Surface #925
Light CC BY-SA 3.0Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
crissXcross #111
Dark CC BY-SA 3.0Dark pattern with some nice diagonal stitched lines crossing over.
Source Ashton
Black Metallic Pattern #1090
Metal CC BY-SA 3.0A free black metallic background pattern. Here's a new pattern I made that looks metallic.
Source V. Hartikainen
Axiom Pattern@2X #331
Grid CC BY-SA 3.0Not even 1kb, but very stylish. Gray thin lines.
Source Struck Axiom
Double Lined #51
Stripes CC BY-SA 3.0Horizontal and vertical lines on a light gray background.
Source Adam Anlauf