Small dogs are great for photography for many reasons, especially dogs under 10 pounds. They're easy to move around, fit in small spaces, and better yet, even easier to frame because you can capture more of their bodies than you could a larger breed's. And you don't even need to have them sit still. If you know cameras well enough or have a fast enough lens and shutter, you can catch some great mid-action shots while you play or do other activities.
Small dogs might not be able to sniff very high, but that doesn't mean you can't hide some treats on the floor for them. Pick a room with a lot of low-level objects, keep them out while you hide the treats, then let them in and let them hunt!
Compared to larger dogs who can look and smell a greater range of heights, small dogs are a bit more limited, but that can also make things more fun. They'll have to stay distracted (say by a toy or treat) or at least listen well enough to stay until you call or whistle, but given their short stature, you should be able to hide up on things where they may be less likely to look, giving you more hiding places than with an average-sized dog.