Background pattern 314 (colour 3) #1837
 Green  CC 0

The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin

 More Textures
Dark Mosaic@2X #122
 Dark  CC BY-SA 3.0

Small dots with minor circles spread across to form a nice mosaic.

Source John Burks

Background pattern 215 (colour 2) #2370
 Blue  CC 0

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

Source Firkin

Glass block pattern #2477
 Brown  CC 0

Produced using the clouds, flames and glass blocks plug-ins in Paint.net and the resulting .PNG vectorised with Vector Magic.

Source Firkin

Cardboard #278
 Paper  CC BY-SA 3.0

A good starting point for a cardboard pattern. This would work well in a variety of colors.

Source Atle Mo

Gray Sand #17
 Dark  CC BY-SA 3.0

A dark gray, sandy pattern with small light dots, and some angled strokes.

Source Atle Mo

Real Carbon Fiber #286
 Carbon  CC BY-SA 3.0

Carbon fiber is never out of fashion, so here is one more style for you.

Source Alfred Lee

Abstract Tiled Background Extended 10 #521
 Noise  CC 0

Abstract Tiled Background Extended 10

Source GDJ

Dark Wood #320
 Wood  CC BY-SA 3.0

A beautiful dark wood pattern, superbly tiled.

Source Omar Alvarado

Handmade Paper@2X #38
 Paper  CC BY-SA 3.0

White handmade paper pattern with small bumps.

Source Marquis

Background pattern 29 #200
 Dark  CC 0

Pattern produced in Paint.net using the Vibrato plug-in.

Source Firkin

Prismatic Chevrons Pattern 5 With Background #469
 Dark  CC 0

Prismatic Chevrons Pattern 5 With Background

Source GDJ

Gold Scale #284
 Light  CC BY-SA 3.0

More Japanese-inspired patterns, Gold Scales this time.

Source Josh Green

Floral pattern 7 (colour 3) #2289
 Pink  CC 0

Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.

Source Firkin

stone filter pack #154
 Stone  CC 0

This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.

Source Lazur URH

Abstract Tiled Background Extended 8 #519
 Noise  CC 0

Abstract Tiled Background Extended 8

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