For this tutorial you are going to need:

20/20
Pixelate Filter

Tutorial number 13.........this is a very colourfull one. I have
tried this tut with darker tones (brown, terra) but those didn't
really work with this tut. But that was my opinion. You might find that
it does work with darker colours......Anyways, this is
the picture I have used:

After opening this picture in PSP go to effects,
plug-in filters, pixelate, sector mosaic and use these settings:

Your picture should look like this:

To make is seamless........save this picture, open in again
in 20/20. In 20/20 go to image, tile effect. Your background is
ready now. It is very 'in your face' now so I suggest you go to
(in 20/20) image, muted background and change the
opacity to 40%. :-)