Blue is the colour, so here is my collection of free blue backgrounds and wallpapers! Very much a mixed bag and ranges from skies to fabric, and from obscure abstract to grunge. I hope you find them useful.
There are also some more in the Christmas images (mostly star related) but it seemed odd having them appear here as this shows the feature or cover image for the entire post. Anyway I left them out from this collection, but it might be worth having a look in there too :)