For this tutorial you'll need:

20/20
Filter Factory A

And this is the image which I have used. Ofcourse you
can use whatever image you want :-)

Now, open the image in PSP and go to effects, plug-in filters,
filter factory a, zoom out and use these settings:

Apply these settings and then your image should look like this:

Save this image and open it in 20/20. In 20/20 go to
image, tile effect and your seamless background is ready. You can
always mute it in 20/20 (image, muted background, 50%) if
you think your background is too loud.