I could stick my neck out and state that it is our sense of sight that is primarily responsible for our impulse purchase decisions. At least our online purchase decisions where the sense of smell, touch, and taste do not enter the picture. That right there is a compelling argument for focusing on the visual element of your site.
What Is Visual Marketing?
Though there is at least one book titled, "Visual Marketing" , there does not seem to be a standard definition or description.

In the world of physical retail, visual merchandising is about floor plans and display shelves. But Visual Marketing is largely accepted as a discipline that encompasses all visual elements of your marketing plan -- be it your logo, template, color scheme, images, websitedesign, and the like.

The Case for Visual Marketing as a Tool for Ecommerce
Ecommerce cannot live without eventually turning to visual marketing. The Internet is all about visual, but only in the last few years has visual marketing come into its own. Now many ecommerce businesses are playing catch up to figure out what it is, and how to do it.

What Are the Tools of Visual Marketing?
A quick and easy response would be: viral videos, memorable graphics, and other visual content. Of course, implementing this is easier said than done. Everyone wants a viral video, but a negligible fraction of videos actually go viral.

Great Visuals Speak the Right Language
You wish to secure more online sales, so you must increase your competitive edge.

One of the most powerful methods is through visuals. Most ecommerce professionals have little to no graphics skills (with due apologies for the stereotyping, of course). Yet, this is one of the absolutely critical aspects of a presentable ecommerce website. At the very least the visual elements of your site should not put off visitors to the point that they abandon your ecommerce website.

When you choose a graphic or create one, make sure it communicates unambiguously. Nothing kills the impact more than having to read the caption to understand the picture. That is not to say that captions cannot be useful in altering a viewer's predictable reaction to a chosen photo. This bait and switch tactic may work in a comedy club, but be cautious about using it in your marketing materials. You never know what kind of a mood the viewer is in and unless your brand reeks of comedy and jabs, it will simply come across as stupid.
What Should Visuals on an Ecommerce Website Communicate?
Communicate emotion, experience, memory, hopes, dreams, intellectual content, relationships, action, purpose, and principle. Before you publish a visual, ask a few others for their reaction. If they have radically different reactions than what you intended to communicate, then you should consider a replacement. Their answers will typically not exactly match yours, but as long as they are in the ballpark you are safe using this visual.

Visual Marketing Can Go Viral
The whole idea behind creating visual marketing is to get the viewers excited about your brand. If they are excited with your visual, they will want to share it with other people. Sometimes your visual marketing will be so amazing that it will threaten to eclipse your brand. That is when the visual goes viral, bearing your brand on its wings.

Rewarding Viewers with Matching Quality E-commerce
When you build good visuals into your site or marketing materials, you must have the product and services to match the quality of your visual content. Visitors will leave immediately if they sense that the actual product or service is weaker than the presentation indicates. So be careful to not simply build powerful visuals while neglecting the substance of your offering.

The point is to sell something useful and desirable to the customer. The visuals can be great, but then the product cannot be trash.
Video as Ecommerce Information Sharing
Many ecommerce businesses are going the YouTube route; trying to promote their brand through information sharing in videos placed on YouTube.com. While this approach can work, there are a couple of points to keep in mind.

Let's say you are selling wedding cakes. You want people to find your website through YouTube videos you produce about wedding tips. After some long hard thinking you have hit on what you predict will be a splendid approach to this topic. You make the video, but it just sits there. What went wrong?

Did you share it with everyone you know? Does the video link back to your site? Attention to the marketing chain prevents a break somewhere along the way. Perhaps the presentation in the video is too bland, plain, dull, or outright boring. Even with an adequate presentation there can be the hindrance of an uninteresting tip. It might be relevant, but if it is uninteresting, then no one will want to share it with anyone else.
Don't Be in a Hurry to Change Your Graphics Overnight
If you are updating your graphics, try not to change too much too soon, or you will alienate your existing customers. Change seems good to you, but from the outside, change severs a critical connection, namely brand recognition. Visuals are powerful connections between ecommerce businesses and customers.