A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
Love me some light mesh on a Monday. Sharp.
Source Wilmotte Bastien
Zero CC tileable hard cover green book, scanned and made by me. CC0
Source Sojan Janso
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
Prismatic Curved Diamond Pattern No Background
Source GDJ
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Lovely pattern with some good-looking non-random noise lines.
Source Zucx
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
A dark pattern made out of 3×3 circles and a 1px shadow. This works well as a carbon texture or background.
Source Atle Mo
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Zero CC tileable cork floor, photographed and made by me. CC0
Source Sojan Janso
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
Prismatic Hypnotic Pattern No Background
Source GDJ
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