I would try sprinkling some corn starch on the stain.Let it set, then brush or vacuum thoroughly.

Have you tried one of the oxygen cleaners? A friend had a light colored recliner that showed where heads rested against it and she mixed a partial scoop of oxyclean with warm water and used a sponge on it. After it dried, she vacuumed it with the soft brush attachment and the head mark is gone.

Good luck!

Thanks for the suggestions.

I'll try the corn starch first but since the headboard is vertical, I'm afraid that there won't be much penetration to speak of.

Re: Oxygen cleaners. I have Oxi-Magic spray but the instructions don't mention its use on upholstery. Seems more for laundry, carpets and hard surfaces.