Add the gallery creator and media uploaders name to mediapress gallery/media.

mpp-display-gallery-media-owner-name.php

<?php
/**
 * Display the name of the creator of the gallery below gallery cover
 *
 */
function mpp_custom_display_gallery_owner_name() {
	$gallery = mpp_get_gallery();

	if ( ! $gallery ) {
		return ;
	}

	printf(  'by: %s',  bp_core_get_userlink( $gallery->user_id ) );
}
add_action( 'mpp_before_gallery_actions', 'mpp_custom_display_gallery_owner_name' );

/**
 * Display the name of the uploader of the media below media thumbnail
 *
 */
function mpp_custom_display_media_owner_name() {
	$media = mpp_get_media();

	if ( ! $media ) {
		return ;
	}

	printf(  'by: %s',  bp_core_get_userlink( $media->user_id ) );
}
add_action( 'mpp_media_meta', 'mpp_custom_display_media_owner_name' );
//display in the lightbox too
add_action( 'mpp_lightbox_media_meta', 'mpp_custom_display_media_owner_name' );