Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
Zero CC tileable hard cover cells book texture, 4k, scanned and made by me. CC0
Source Sojan Janso
Prismatic Groovy Concentric Background
Source GDJ
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
Zero CC tileable cork floor, photographed and made by me. CC0
Source Sojan Janso
This is the remix of an OCAL clipart called "Art Nouveau ornament" uploaded by "microcosme".Thanks.This is a seamless pattern of an Art Nouveau ornament.
Source Yamachem
A bit simplified version. Although it could be edited out to be simpler. Anyway, this time the tiling is converted to a pattern fill -which is using clipping for the tile's edges.
Source Lazur URH
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Prismatic Geometric Tessellation Pattern 4 No Background
Source GDJ
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Prismatic Curved Diamond Pattern 4 No Background
Source GDJ
This is the remix of "blue wave-seigaiha".This is the flowers of pink silk tree which is called "nemuno-ki".About pink silk tree ,refer to here:https://jp.pinterest.com/pin/500744052301210439/
Source Yamachem
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
The name alone is awesome, but so is this sweet dark pattern.
Source Federica Pelzel
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
The image depicts a seamless pattern made using a bird's face.
Source Yamachem