This light blue background pattern is quite pleasing to the eye, it consists of a tiny rough grid pattern, which is seamless by design. That's it, if you like the color, you can use this seamless pattern in a web design without making any further modifications to it.
Source V. Hartikainen
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
Bright Multicolored Floral Background by Karen Arnold from PDP.
Source GDJ
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
Here's an yet another seamless note paper texture for use as a background on websites.
Source V. Hartikainen
Uses spirals from Pixabay. To get the basic tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Heavily remixed from a drawing that was uploaded to Pixabay by ractapopulous
Source Firkin
A free tileable background colored in off-white (antique white) color.
Source V. Hartikainen
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
Zero CC tillable hard cover red book with X shape marks. Scanned and made by me.
Source Sojan Janso
Here's a new background image for websites with a seamless pink texture. It should look beautiful with website themes where light pink background is needed. The background is seamless, therefore it should be used as a tiled background.
Source V. Hartikainen
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
A nice and simple gray stucco material. Great on its own, or as a base for a new pattern.
Source Bartosz Kaszubowski
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
The edges of all the red objects line up either vertically or horizontally, but it doesn't appear so. Made from a square tile that can be got by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
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
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin