functions.php

add_filter( 'soliloquy_fc_query_args', 'rover_save_soliloquy_query', 1, 3 );
function rover_save_soliloquy_query( $query_args, $id, $data ) {	
	// Only show posts with featured images
	$query_args['meta_query'] = array(
		array(
			'key' => '_thumbnail_id',
		)
	);
	
	return $query_args;
}