Diamond pattern (colour 7) #2274
 Red  CC 0

From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin

 More Textures
Floral design 91 #1814
 Dark  CC 0

From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.

Source Firkin

Prismatic Geometric Tessellation Pattern 4 No Background@2X #558
 Noise  CC 0

Prismatic Geometric Tessellation Pattern 4 No Background

Source GDJ

Cross Stripes@2X #48
 Dark  CC BY-SA 3.0

Nice and simple crossed lines in dark gray tones.

Source Stefan Aleksić

Small Crosses@2X #116
 Stripes  CC BY-SA 3.0

Sharp pixel pattern looking like some sort of fabric.

Source Dmitry

Seamless Colorful Floral Pattern Background #256
 Fabric  CC 0

PDP

Source GDJ

Green Dust & Scratches #107
 Wall  CC BY-SA 3.0

Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.

Source Atle Mo

Prismatic Isometric Cube Extra Pattern No Background #405
 Light  CC 0

Prismatic Isometric Cube Extra Pattern No Background

Source GDJ

Background pattern 328 (colour 6) #1796
 Red  CC 0

To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i

Source Firkin

Colorful Paw Prints Pattern Background #260
 Noise  CC 0

pixabay.

Source GDJ

Background pattern 227 #2314
 Yellow  CC 0

A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.

Source Firkin