This is actually an article I wrote for my internship this summer. It discusses why a company should be interested in using instagram, since a lot of the work I did dealt with social media and the use in companies, but also why pictures are so important to a website and it's success.
It's a known fact that pictures spark more interest in consumers, as it adds a face to your otherwise faceless brand. They create the bridge that fills the gap between brand and human. This often can garner trust into your brand, as a person is more likely to trust a person (or company) with whom/which they feel personally connected over one that is just a name on the web. Pictures get more "likes" on Facebook than do strictly text posts and are often found to be more memorable.
This dips into the realm of research because you must look into what your audience yearns for most-- text, pictures, videos. There have been many studies already done to see what type of information sparks the most response and what kind of responses. In today's world it isn't just about knowing what it is that your audience desires, but you have to be the best provider of that product or service. Pictures, and instagram, are ways that elicit emotion and help researchers understand what makes their audiences tick. This is often a mystery question, as to how to get these emotions to come about, but pictures are an easy way to judge reactions without having to actually be present to survey viewers or consumers. For example, if you release a sneak peak of an advertisement for a new soup that contains a picture of 3 adorable children and another that contains an image of a middle-aged person alone, you will most likely get more likes on one than the other, and that is what hits home and is the winner with your target market.
Pictures are another qualitative component that can drastically improve research responses. You can also gain quantitative data from sites like Facebook or Twitter, as you can compare numbers of likes, comments, or shares on Facebook and a person can track retweets and favorites on Twitter. The combination of both types of data from one source, pictures, is incredibly efficient and valuable to brands everywhere.