This seamless background image should look nice on websites. It has a dark blue gray texture with vertical stripes, it tiles seamlessly and, like all of the background images here, it's free. So, if you like it, take it!
Source V. Hartikainen
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
The starting point for this was a texture drawn with the 'Radial Colors' plug-in in Paint.net.
Source Firkin
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
Prismatic Geometric Pattern Background No Black
Source GDJ
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Bumps, highlight and shadows – all good things.
Source Badhon Ebrahim
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
A seamless pattern formed from a sports car on clker.com. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
Prismatic Abstract Background Design
Source GDJ
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Light gray paper pattern with small traces of fiber and some dust.
Source Atle Mo
A very dark spotted twinkle pattern for your twinkle needs.
Source Badhon Ebrahim
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ