Sand your old wood furniture with a fine-grit sandpaper. Wipe up dust and debris with a damp rag. The wood does not have to be perfect, but sanding it will help the decoupage medium to adhere better for a longer lasting finish.
Get some paper similar in color to what you want your finished leather to look like. For a light brown paper, use brown paper bags. Achieve other colors with tissue wrapping paper. Tear the paper into random chunks about the size of your hand for large, flat surfaces, or smaller 2- to 3-inch pieces for small, narrow surfaces. Tear them so they are all uneven -- the more rugged and crooked the edges, the better. Throw them in a container or basket so they’ll be easy to grab while you work.
Remove hinges and hardware. Cover any parts of your furniture that you do not want covered with a leather look. Use painter’s tape and plastic garbage bags to shield upholstery or paint jobs that you wish to preserve.
Wet a paintbrush, then squeeze it to remove excess water so it doesn't drip. Dip it in your decoupage medium.
Brush some decoupage medium on your surface to cover an area larger than your chunks of paper. Grab a paper chunk and lay it on the medium, pressing it down flat. If you’ve dabbled in decoupage before, you might be tempted to smooth the paper out, but when re-creating a faux leather look, you want the paper to stay somewhat wrinkled.
Brush more medium on the wood, overlapping the edges of the last piece of paper. Grab another piece of torn paper and lay it on. Let it overlap the first piece. Continue this method to cover all areas you wish to appear leathery and until you like the look of the surface. Let it dry according to the manufacturer's instructions.
Pour a few drops of acrylic paint in a disposable container. Use brown for creating an aged, weathered look. If you prefer, use the same color as your tissue but a couple of shades darker. The same color in a darker shade will not make it look as weathered, but it will help add depth to it and bring out the texture.
Dab the tips of the bristles of a dry paintbrush into the paint, then immediately brush it back and forth on some scrap paper until the paint is almost all wiped off. Brush over some of the faux leather areas at random, with quick but light back-and-forth strokes. This technique is called “dry brushing” and you can continue it until you’re satisfied with the coloration of your leather.
Let the acrylic paint dry for a few minutes. Brush more decoupage medium over the entire leathery surface to seal it.