I was trying to show size on my pieces and not liking a yard stick that has a distracting color to my piece so my solution was to take a piece of foam core that I marked inches on the side and inches across the bottom.
Here is an example of it. Not too professional looking yet but it gets the size visually. Oh! I just had thought. I think there is quilters tapes that are in measurements maybe if they have white I might try it.