This beige background pattern resembles a concrete wall with engravings or something similar to it.
Source V. Hartikainen
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Medium gray pattern with small strokes to give a weave effect.
Source Catherine
A seamless pattern formed from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Triangular Background Design Mark II 5
Source GDJ
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Coming in at 666x666px, this is an evil big pattern, but nice and soft at the same time.
Source Atle Mo
Fake or not, it’s quite luxurious.
Source Factorio.us Collective
From a drawing in 'Heroes of North African Discovery', Nancy Meugens, 1894.
Source Firkin
The original enhanced with some gradients.
Source Firkin
Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857
Source Firkin
This texture looks like old leather. It should look great as a background on web pages.
Source V. Hartikainen
A version without colours blended together to give a different look.
Source Firkin
A free seamless background with pink spots.
Source V. Hartikainen
f you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
A brown seamless wood texture in a form of stripe pattern. The result has turned out pretty well, in my opinion.
Source V. Hartikainen
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Formed from decorative divider 184 in paint.net. Vectorised with Vector Magic.
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas