If you are using both product images and product options image, we suggest you to use radio button instead of selectbox as your product option type and do not set the default value so that the product images are not automatically changed to product option image.
Before select product option:
After select product option:
1. Select the radio option type.
Step B and C:
1. Do not check this option as it will set the option as the default one.
2. Add the image that will be used as the product option image