Topic: background image (tiled) instead of black/grey ?

Any idea how to use a background image, not just 1 but tiled?
I really like my background image which is tiled on my website but when linking to my gallery page it goes to the default dark grey or black. I
have tried inserting the background image with some success but it is just the one image, any idea how to make it tiled like my site?
Any help, suggestions or advice would be greatly appreciated.
Cheers,
Phil