An old work for a new style! When someone says decoupage today, I am not sure they mean the old style 1970's or the new style called "collage or mixed media". It is difficult today to tell if something is vintage, or new made to be vintage and gruny.
When I was in collage, I did collage in the late 1970's and it is not the collage we are doing today. I had to use magazine pictures and have them compliment each piece with the color hues, patterns, texture...Today, I get to do the same perhaps or not. I can grunge them up with gesso, acrylic paints, stains, wax, hammer and nail holes, old papers, tissue papers, music and vintage books, and everything else you can collect in a box.
Cut, rip and glue. Use white elmsers glue mixed with water to be thin, use decoupage brand glue, use various mediums by golden or other companies. Your inks, your brown umber or sienna acrylic can be used to grunge up and antique. You can use tea and coffee to fade items including ribbon to make vintage galore!