Mirrored Squares@2X #124
 Dark  CC BY-SA 3.0

Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.

Source Atle Mo

 More Textures
Background pattern #2000
 Dark  CC 0

Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin

Retro Circles Background 4 No Black@2X #423
 Dark  CC 0

Retro Circles Background 4 No Black

Source GDJ

Checkered Light Emboss #280
 Grid  CC BY-SA 3.0

Sort of like the Photoshop transparent background, but better!

Source Alex Parker

fishnet 01 #2475
 Grid  CC 0

The image depicts a seamless pattern of a fishnet with a plenty of fish.It may be a lucky charm for fishermen.

Source Yamachem

Carbon Fiber v2@2X #106
 Carbon  CC BY-SA 3.0

One more updated pattern. Not really carbon fiber, but it’s the most popular pattern, so I’ll give you an extra choice.

Source Atle Mo

Diamond pattern (colour 6) #2280
 Yellow  CC 0

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

Source Firkin

Background pattern 259 (colour 6) #2097
 Blue  CC 0

Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin

Diamond pattern (colour 9) #2269
 Fabric  CC 0

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

Source Firkin

Abstract Tiled Background Extended 6 #517
 Noise  CC 0

Abstract Tiled Background Extended 6

Source GDJ

Subtle Orange Emboss@2X #98
 Light  CC BY-SA 3.0

A hint of orange color, and some crossed and embossed lines.

Source Adam Anlauf

Background pattern 263 #2073
 Pink  CC 0

Actually remixed from a pattern on Pixabay. But then noticed a very similar one on Openclipart.org uploaded by btj51q2.

Source Firkin

Street Art Pattern #1196
 Concrete  CC BY-SA 3.0

Looks as if it's spray painted on the wall. You can be sure that this pattern will seamlessly fill your backgrounds on web pages.

Source V. Hartikainen

Colorful Floral Background 3 No Black #485
 Light  CC 0

Colorful Floral Background 3 No Black

Source GDJ

Background pattern purple #1998
 Colorful  CC 0

Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin

Prismatic Curved Diamond Pattern 4 No Background #541
 Diamond  CC 0

Prismatic Curved Diamond Pattern 4 No Background

Source GDJ