One underused area of photography that I think businesses could utilise more to attract attention to their online presence is macro photography. 
Seeing the world in miniature seems to gain immediate attention and encourage people to look at your content that might not otherwise be inclined to take a look. This is because macro photography offers a way for people to see the world from a completely different perspective.
This is only my opinion of course and I'd be interested to hear what people's thoughts are on this so please leave a comment.