If you want a decorated inside, just put the same piece of paper through the printer twice:
The first time through it prints on the inside (background) and
the second time through it prints on the front side (pattern - box, bag, etc.) of the page.
INSTRUCTIONS (FOR HP PRINTERS)
First, print out the background - SIDE A.
Put the paper in the lower (IN) tray.
Make sure there's no paper in the upper (OUT) tray.
Put the printed page- SIDE A - back in the lower (IN) tray of the printer and print the B side out - B side would be anything with the pattern, a gift bag, box...