More Textures
Background pattern 239 #2218
 Dark  CC 0

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

Source Firkin

Batthern #324
 Grid  CC BY-SA 3.0

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

Source Factorio.us Collective

Colorful Floral Background 2 #487
 Dark  CC 0

Colorful Floral Background 2

Source GDJ

Ravenna #354
 Wall  CC BY-SA 3.0

I guess this is inspired by the city of Ravenna in Italy and its stone walls.

Source Sentel

Background pattern 235 #2255
 Yellow  CC 0

To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.

Source Firkin

Colorful Geometric Pattern Background #231
 Noise  CC 0

PDP

Source GDJ

Retro Squares Background 2@2X #417
 Noise  CC 0

Retro Squares Background 2

Source GDJ

Concrete Wall 2@2X #80
 Wall  CC BY-SA 3.0

A light gray wall or floor (you decide) of concrete.

Source Atle Mo