Real snow that tiles, not easy. This is not perfect, but an attempt.
Source Atle Mo
Another fairly simple design drawn in Paint.net and vectorized in Inkscape.
Source Firkin
Seamless Dark Grunge Texture. Here's a new grunge texture for use as a background.
Source V. Hartikainen
You may use it as is, or modify it as you like.
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
Zero CC tileable pine bark texture, photographed and made by me. CC0
Source Sojan Janso
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
It’s a hole, in a pattern. On your website. Dig it!
Source Josh Green
An abstract pale yellow paper-like background with stains colored in yellow and green.
Source V. Hartikainen
The image is a remix of "edo pattern-samekomon".I changed the color of dots from black to white and added BG in light-brown.
Source Yamachem
The image depicts a seamless pattern made using a bird's face.
Source Yamachem
A free seamless background pattern for use on websites.
Source V. Hartikainen
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
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
A seamless pattern formed from background pattern 102
Source Firkin
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
Bit of a strange name on this one, but still nice. Tiny gray square things.
Source Carlos Valdez
A free seamless background with pink spots.
Source V. Hartikainen
Prismatic Groovy Concentric Background No Black
Source GDJ
Here's a bluish gray striped background pattern for use on web sites.
Source V. Hartikainen
Floral patterns might not be the hottest thing right now, but you never know when you need it!
Source Lauren