Artangel: Mixed media crumpled tissue technique - tutorial - basically, glue tissue paper over a canvas, let dry. Paint, let dry, then rub pastel or chalk over the surface to highlight the texture. Would be an awesome way to vignette around a painting.
Bubble Printing: cup of water, 2 Tablespoons of paint, and a few squirts of dish soap in each container. Blow with a straw into the cup to make lots of bubbles pile up on top of the cup - then press paper to the bubbles so they pop and leave bubble prints