Sometimes I draw pen sketches and I don't want to paint, but I want color on the page. I've written about this before, but in case you missed it, this is what I like to do—collage around the drawing.
I took a piece of 140 lb. watercolor paper that I had painted (and used for covering one of my journals) and cut a strip out to wrap around the image. (It doesn't cover anything on the page as the drawing didn't extend there, but this is also useful if you want to crop your drawing in some way after the fact!)
If you want to see more examples of this go to the category list in the left column of the blog and click on "Collage" and browse. Then get busy and cut up some paper!