Maybe this will help:
Open any photoprogramm and make a new picture at the size you need.
Warning: If it is NOT the good size, it wont work later ( or could) make
problems in the PDF settings ( if you are using that to distiller).
22 x 30.3 in centimeters at 300 DPI is what I have as standard A4.
Make the color you want and safe as jpeg, comprress to several levels. In
this case level 3 will do.
Save also as Tiff as backup, because you can open that any time without
loosing information of the picture.
In publisher, go to Format / background
it opens the regular color system.
Klick MORE BACKGROUNDS, and after that opens, select PICTURE.
Insert from the harddisk that picture ( the JPG in this case, not the tiff)
You can now select either if you want this for only one page or all.
Hope this is what you are looking for.
If it is, you can make any time the same picture as background or make even
your own layout as a background ( compilation).
If you have problems later, it only will while printing.
Therefore THIS size is tested by me. Bigger will give problems.
If there is any, then at the printer settings try A3 and distill to PDF
first.
It shows the page precies, only with the white paper around it.
that is not a problem for commercial printers at all.
Or.....make a new size A4 in the PRINTER settings and add space extra, than
the same result shows as at the A3,
Regards,
Karel