Lead glass tile #2048
 Colorful  CC 0

Mostly just mucked about with the colours and made one of the paths in the lead frame opaque. The glass remains transparent.

Source Firkin

 More Textures
Wine waiter pattern #2403
 Colorful  CC 0

A seamless pattern formed from a square tile based on a jpg on Pixabay. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.

Source Firkin

Background pattern 215 (colour 4) #2368
 Green  CC 0

A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.

Source Firkin

Old Mathematics@2X #44
 Stripes  CC BY-SA 3.0

This one takes you back to math class. Classic mathematic board underlay.

Source Josh Green

Diamonds Are Forever #183
 Diamond  CC BY-SA 3.0

Sharp diamond pattern. A small 24x18px tile.

Source Tom Neal

Connected@2X #349
 Light  CC BY-SA 3.0

White circles connecting on a light gray background.

Source Mark Collins

Prismatic Abstract Geometric Background 5 No Black #402
 Noise  CC 0

Prismatic Abstract Geometric Background 5 No Black

Source GDJ

Food and drink design #1897
 Dark  CC 0

Colour version that is close to the original drawing uploaded to Pixabay by pencilparker.

Source Firkin

Background pattern 270 #2061
 Dark  CC 0

A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin

Prismatic Hexagonalism Pattern No Background #391
 Light  CC 0

Prismatic Hexagonalism Pattern No Background

Source GDJ

Polonez Pattern #334
 Gray  CC BY-SA 3.0

A car pattern?! Can it be subtle? I say yes!

Source Radosław Rzepecki

Carbon Fiber Big #326
 Carbon  CC BY-SA 3.0

Bigger is better, right? So here you have some large carbon fiber.

Source Factorio.us Collective

Dotnoise Light Grey@2X #309
 Wall  CC BY-SA 3.0

Sort of like the back of a wooden board. Light, subtle, and stylish, just the way we like it!

Source Nikolalek