I've never thought about it before, but I've consistently used "image" ever since I learned about the <img> tag as a kid. It's very interesting that you can segment groups by which word they use.
I'm the same way, also thanks to [img] in BBCode. For what it's worth I was also a heavy ImageShack user and always avoided PhotoBucket. I wonder if there's any relation :p
The HTML5 <picture> tag makes that variation a lot more relevant. The "photo" people are also implicitly talking about art direction! Photos are almost always a "page content" thing, then I see people talk about generating "images" and "pictures" for their website's pixel-perfect UI/navigation/logo needs.
