Take all your photographs (and any other information) to your nearest regimental/military museum, and ask the staff if they can help with identification. It doesn't matter if it turns out that your husband's grandfather wasn't in the museum's regiment, they will give as much help as they can. I know a woman who took photos of her late uncle to the Green Howards Regimental museum in Richmond (N. Yorks.) to ask about the medals that he was wearing, and the staff identified all the medals, just from a photo. Best of luck.