Please add Media player built in look like a 'VLC Media player', add documents viewer that supports Power point files, PDF files, word files that increases your users base and it lead for increase your revenue. In addition you must add password/passcode for security purposes; In 21th century privacy and security must be needed by users.
Above mentioned feature leads to increase your user base that takes 'solid explorer' to next level like 'Nova Launcher' is famous among Android users.