Batthern@2X #325
 Grid  CC BY-SA 3.0

Sometimes simple really is what you need, and this could fit you well.

Source Factorio.us Collective

 More Textures
Checkered Pattern@2X #323
 Grid  CC BY-SA 3.0

Simple gray checkered lines, in light tones.

Source Radosław Rzepecki

Background pattern blue #1955
 Blue  CC 0

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

Source Firkin

Background pattern 308 (colour 3) #1870
 Colorful  CC 0

Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.

Source Firkin

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

Retro Circles Background 4 No Black

Source GDJ

Background pattern 117 #524
 Noise  CC 0

A seamless pattern drawn originally in Paint.net by distorting a slice of background pattern 116 and copying the resulting triangle numerous times.

Source Firkin

Diamond pattern 2 (colour 2) #2267
 Colorful  CC 0

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

Source Firkin

Background pattern 208 (colour 2) #2462
 Grid  CC 0

A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.

Source Firkin

Connected #348
 Light  CC BY-SA 3.0

White circles connecting on a light gray background.

Source Mark Collins

Background pattern 21 #205
 Light  CC 0

A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.

Source Firkin

Retro Squares Background 9 #399
 Dark  CC 0

Retro Squares Background 9

Source GDJ

Dark Brick Wall@2X #136
 Wall  CC BY-SA 3.0

Black brick wall pattern. Brick your site up!

Source Alex Parker

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

Floral Pattern Background 3 #218
 Noise  CC 0

PDP

Source GDJ

Prismatic Polka Dots Mark II 3 No Background@2X #535
 Noise  CC 0

Prismatic Polka Dots Mark II 3 No Background

Source GDJ