-- https://makandracards.com/magento/16457-importing-images
-- to import images you first need these columns:
_media_attribute_id - the attribute_id of media_gallery (see below)
_media_image - the path of the image, i.e. /some_image.jpg
_media_lable - the image label, i.e. "My nice image"
_media_position - the position, 1, 2 etc
_media_is_disabled - whether the image is excluded from the gallery or not
_media_attribute_id is the most important field, it needs to correspond to the media_gallery attribute id, you can find this out by running this SQL:
select attribute_id from eav_attribute where attribute_code = 'media_gallery';
-- When you have this structure set up correctly, you can put all your iamges in media/import and you're all done!
-- If you want to use any of the images as the image, small_image or thumbnail
-- then just add the same path you entered in _media_image in the column for the
-- relevant image.