It is not possible to export other images to the marketplace than the images that are imported by into EffectConnect. This is because EffectConnect is sending your product information on the way it's received from your webshop or data source.
It may be possible though to manually change the images on the marketplace by your needs and wishes, but please keep in mind that EffectConnect can re-send your original images to the marketplace which overwrites your manually added images. To avoid this, you could disable the product synchronization for this specific product.
Our advice is if you would like to change your images on the marketplace, to change the images in your webshop or data source. In this way, EffectConnect will import the newly added images and automatically send them to the marketplace if you've created a product mapping for these products.