If you have a product that comes in different sizes, shapes, or styles, Shopify's image variants feature can allow you to show them all easily on the same product page. When customers want to see the different styles of one of your products, the image will change accordingly as they pick different options from the product's dropdown menu. If you already have product variants set up and you just need to add variant images, you can skip to the adding variant images section.
Creating a new product with variants
When creating a new product, you can enable variants by checking the This product has multiple options box just below the Inventory policy section. After checking the box, a new section will appear that allows you to pick the ways in which your product variants will differ. Option Names let you choose from title, color, size, material, style, or custom, and Option Values let you put in any attribute you want.
Adding variants to an existing product
Before adding a variant to an existing product, make sure you know which product options you want to highlight (such as title, color, size, material, style, or a custom value), and click the edit options link to add them.
Then select the Add a variant button and fill in the information for your new product variant.
Adding variant images
After you've created your product variants, each one will appear in a list in the product's inventory and variants section. You can add images to each one by clicking on the camera icon next to the variant attributes. If your product variant already has an image associated with it, you can change the image by clicking on the image instead of the camera.
Clicking on the camera or image thumbnail will bring up the Select variant image dialog box, where you can choose an image from your existing images or upload a new image.
Choose the image you'd like to associate with your variant and click the Save button in the bottom right-hand corner to return to your variants list.
Adding variant images to multiple product variants at once
If you have many variants that require the same image, add them all at once by filling in the variants' checkboxes and clicking on the Bulk actions option that appears.
Then use the Update images link to access the Select variant images dialog box and change the images for the selected product variants.
Saving your product variants
After this, scroll to the bottom of the product's information page and click the Save button in the bottom right-hand corner to return to your products list. The product variants will now be live in your store.
Keep your product photography consistent
Because users can easily switch from image to image, it is important to make sure that the transition is almost invisible. This is best achieved if the uploaded photos are exactly the same size and were composed in the same way. Smashing Magazine has a great article with examples of and tips for better product photos. Shopify has also created a concise guide to image sizes and aspect ratio, which makes your product images look consistent even when they're not the same size.