Make sure you remember to add words to this effect.
Where an image is incorporated in products for sale, the purchased image may not constitute the main value of the end product. For example, images cannot be sold as framed prints, postcards, greeting cards, posters or similar where the image would be considered the end product.
You might find something of use at The Association of Photographers website. Just click on the AOP Latest button and scroll down to the bottom of the page (or just click here)