Zero CC tileable grass texture, photographed and made by me. CC0
Source Sojan Janso
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
Prismatic Abstract Geometric Background 5
Source GDJ
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
Never out of fashion and so much hotter than the 45º everyone knows, here is a sweet 60º line pattern.
Source Atle Mo
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
This one is quite simple in design, it consists of vertical stripes layered on top of a seamless texture.
Source V. Hartikainen
A seamless gray background texture suitable for use on websites. To me, it has the look of stone. Feel free to modify it to meet your needs (by making it a bit lighter or darker, for example).
Source V. Hartikainen
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Love me some light mesh on a Monday. Sharp.
Source Wilmotte Bastien
From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo