"Black Metal Grid", Seamless Background Pattern #1080
 Metal  CC BY-SA 3.0

A free seamless background pattern for use on websites.

Source V. Hartikainen

 More Textures
HIXS [email protected] #610
 Dark  CC BY-SA 3.0

Heavy depth and shadows here, but might work well on some mobile apps.

Source Damian Rivas

Wavy background #2021
 Pink  CC 0

CC0 and a seamless pattern from a tile drawn in Paint.net .

Source SliverKnight

Redox [email protected] #850
 Light  CC BY-SA 3.0

Bright gray tones with a hint of some metal surface.

Source Hendrik Lammers

Lock and key pattern #1884
 Yellow  CC 0

Seamless pattern formed from a key and lock.

Source Firkin

Polyester Lite #837
 Light  CC BY-SA 3.0

A tiny polyester pixel pattern.

Source Jeremy

Dark Wall #817
 Dark  CC BY-SA 3.0

Just to prove my point, here is a slightly modified dark version.

Source Atle Mo

White Linen #839
 Light  CC BY-SA 3.0

Dead simple but beautiful horizontal line pattern.

Source Fabian Schultz

[email protected] #676
 Diamond  CC BY-SA 3.0

I’m guessing this is related to the Sony Vaio? It’s a nice pattern no matter where it’s from.

Source Zigzain

Satin [email protected] #1045
 Light  CC BY-SA 3.0

Super simple but very nice indeed. Gray with vertical stripes.

Source Merrin Macleod

Floral pattern 8 #2096
 Colorful  CC 0

Remixed from a pattern on Pixabay

Source Firkin

Prismatic Dots Background [email protected] #514
 Dark  CC 0

Prismatic Dots Background 7

Source GDJ

Always [email protected] #54
 Dark  CC BY-SA 3.0

Crossing lines with a subtle emboss effect on a dark background.

Source Stefan Aleksić

Seamless Core Pattern 5 #169
 Dark  CC 0

Seamless Core Pattern 5

Source GDJ

Paisley #1343
 Light  CC BY-SA 3.0

The name Paisley reminds me of an old British servant. That’s just me.

Source Swetha

Prismatic Arrows [email protected] #802
 Noise  CC 0

Prismatic Arrows Background

Source GDJ

Stone Wall & Light Green #1537
 Stone  CC 0

Incoming catena. Stone & well. CC0 texture.

Source Unknow

Seamless Core Pattern 4 #168
 Dark  CC 0

Seamless Core Pattern 4

Source GDJ

Fabric pattern (colour 5) #2398
 Fabric  CC 0

Alternative 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

"Beige Stone", Seamless Web Texture #1031
 Stone  CC BY-SA 3.0

It looks like a polished stone surface to me. Download it for free, as always.

Source V. Hartikainen

Prismatic Dots Background 2 #503
 Noise  CC 0

Prismatic Dots Background 2

Source GDJ

Prismatic Polka Dots Mark II 2 No Background #532
 Noise  CC 0

Prismatic Polka Dots Mark II 2 No Background

Source GDJ

Element of beach pattern with background #254
 Noise  CC 0

Element of beach pattern with background.

Source Rones

Dark [email protected] #818
 Dark  CC BY-SA 3.0

Just to prove my point, here is a slightly modified dark version.

Source Atle Mo

Random Binary Background #274
 Light  CC 0

Random Binary Background

Source GDJ

Mix & Gray Pattern #1631
 Metal  CC 0

Metal-Plain or Painted. CC0 License.

Source Unknow

Prismatic Isometric Cube Wireframe Pattern No [email protected] #500
 Light  CC 0

Prismatic Isometric Cube Wireframe Pattern No Background

Source GDJ

Colorful Floral Background 3 #483
 Dark  CC 0

Colorful Floral Background 3

Source GDJ

Small Crackle [email protected] #353
 Light  CC BY-SA 3.0

Light gray pattern with an almost wall tile-like appearance.

Source Markus Tinner

[email protected] #1108
 Light  CC BY-SA 3.0

A series of 5 patterns. That’s what the P stands for, if you didn’t guess it.

Source Dima Shiper