I have occasionally used an innovative textural background in my watercolor paintings, which has the effect of giving them a timeless sepia-toned look. I have used this technique primarily for portrait paintings and my construction rubble series. In fact, I discovered the effect accidentally years ago while trying to get an interesting, clay-like background for my rubble paintings. I would like to describe it for you here, especially for my students, who are currently using this technique. I call it the "rivulet technique"
Here are some samples showing the "Rivulet Technique":
My students are ARThouse are currently exploring this technique. It is tricky to do and relies upon utilizing the correct earth colors, such as raw or burnt umber. Actually I wrote an article about the technique for "The watercolor Page" of American Artist magazine back in 1986! For old times sake, here is the original article, click on a thumbnail, and then click the "Image From" text near the bottom to be able to zoom in to read them.