A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Zero CC tileable ground (#2) cracked, crackled texture, made by me. CC0
Source Sojan Janso
Dark and hard, just the way we like it. Embossed triangles makes a nice pattern.
Source Ivan Ginev
The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This background pattern contains a seamless texture of bark. It's not very realistic, but I think it looks quite nice.
Source V. Hartikainen
Number five from the same submitter, makes my job easy.
Source Dima Shiper
A fun-looking elastoplast/band-aid pattern. A hint of orange tone in this one.
Source Josh Green
Prismatic Groovy Concentric Background 4
Source GDJ
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin