Foremost the icon should be consistent with other popular websites and that does not take a toll on your originality. Instead it makes them easier to locate and also reflect their purpose. The most commonly used icons by ecommerce websites are the trolley or hybrid trolley which almost always are consistent with add to cart/add to basket options. They can be later modified to have an upper or lower threshold of items added. There are other websites and channels which ubiquitously use the sharing icons. They are majorly comprised of social networking websites like Facebook, Twitter and Instagram. But they can also be customized to suit the background and theme of the website.
Flexibility always Matters-
Any good icon for digital designing should be amicable to customization, should have a choice of colors and most importantly should be movable. Make sure your icon has multiple fonts and balancing options which make them visible and noticeable at a glance. Too many fonts clutter your website, so plan ahead and eliminate unwanted icons from beforehand. Most importantly, make them relevant to your target guests/visitors/customers.