How do I upload one picture for multiple variant options?

So the first image you upload with Photo Finish is really important in Shopify it's called the featured image. It's the first picture that shows up in the product gallery and it's also the image that shows up in the cart in checkout and on the order confirmation emails. 

So at Photo Finish we use this principle for variants.

So you can upload one photo to your first Variant SKU and it will represent all the other variants in both the cart and in checkout  

So if the product looks like this:

Blue T Shirt
Color: Blue SIze: Small
SKU: 1234-S
Color: Blue SIze: Medium
SKU: 1234-M
Color: Blue SIze: Large
SKU: 1234-L
Color: Blue SIze: XL
SKU: 1234-XL

You would only have the picture named: 1234-S.jpg

If you had multiple pictures to add to the gallery then I would do:
1234-S_1.jpg
1234-S_2.jpg
1234-S_3.jpg
etc. etc.

We are only suggesting using the first variant as that's an easy rule you can use going forward but in reality any of the SKU's would work.

As mentioned above the default behavior for Shopify is such that if there isn't a variant image that's matched up Shopify will use the featured image by default. 

Here's an example of this in practice:

So we only added the photos to the top variant just like I'm explaining above.

However, when the customer goes to put it in the cart the White Size 6 which doesn't have a variant image:

However, Shopify defaults to the featured image in both the cart and the checkout:

So you've only got to import one variant image and it will work all the way through checkout.