I'm not a lawyer, but here are my thoughts:
If you obtained the photo from a source such a Sheila's website, then the photo is the property of the source...You may, or may not, need permission to use it, but I think you'd be safe by including wording at the bottom of the picture that states, "Photo courtesy of Sheila Landry Designs website;
www.sheilalandrydesigns.com".
On the other hand, if you made one of Sheila's designs and took a photo of it, then you own the photo of the work that you did...In this case, I don't think you'd need any disclaimer in your "catalog".
I think that the real area of concern is when it comes to the pattern itself...Some source's, such as Steve's, allow you to use his patterns for any purpose (personal, or for profit), but you are not allowed to sell the pattern, nor redistribute it...Other sources have other rules, and I think that's where all of the copyright types of questions come into play.