You can export your parent SKUs and assign them an unlimited number of images. By assigning all available images to the parent, you will not need to assign images to children. Because all images are inherited from parent to children automatically.
You may also find it useful to label the images.
This feature can be used for single or children items also.
Here are the steps you need to follow:
1- Go to Inventory>Products, call and select your products. You can also add a filter to display only parents if you want to update multiple parents only.
2- Download the file from the Notifications from the top right.
These are the fields in the exported file.
Right now, this parent has 1 image. You can add an unlimited number of images by using parent sku (in column A) for each line and adding new image urls for each line(column B).
You can also add labels to the images (column C).
3- After making your changes to the products, you can upload the file back into the SA.