This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
Prismatic Hexagonalist Pattern No Background
Source GDJ
A background pattern with wavy green vertical stripes. This one has green stripes on a white background. Download if you like it.
Source V. Hartikainen
Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
A seamless pattern based on a rectangular tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A seamless canvas texture for using as background on websites. Colored in pale tones of brown.
Source V. Hartikainen
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
This one needs to be used in small areas; you can see it repeat.
Source Luca
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Remixed from a drawing in 'A Girl in Ten Thousand', Elizabeth Meade, 1896.
Source Firkin
Zero CC tileable ground (#2) cracked, crackled texture, made by me. CC0
Source Sojan Janso
Prismatic Hexagonalist Pattern No Background
Source GDJ
Zero CC tileable Laminate wood texture, photographed and made by me. CC0
Source Sojan Janso
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo