For a bundle product, M2E uploads images from the main (parent) product.
1) Description Settings
...
Main Image – uploads the largest image of your eBay item from the main (parent) product.
Super Size – displays larger, more detailed pictures (up to 800w x 800h pixels - 800 pixels on the longest side). This feature may come with an additional fee.
Default Image Url – if a product does not have the Main Image this image will be shown instead.
Gallery Images – adds up to 11 additional images from the main (parent) product. They will appear as small thumbnails under the Base large image.
Change Images for Attribute (only for Configurable products) – Not needed for Bundle products.
...
The image shows how M2E will upload product images according to the settings above.
...
3) Images on eBay
...