digiKam - Professional Photo Management with the Power of Open Source
REPOST IT! FOR INSTAGRAM - REPOST IT! FOR INSTAGRAM is an easy-to-use app by Digi set though which you can schedule desired posts to upload them on Instagram automatically.
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
Apphi - Apphi – Schedule Posts for Instagram is a Free to Use Mobile Application that automatically posts your scheduled Instagram photos and videos.
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
Repost FOR Instagram - Repost FOR Instagram is a social app that enables you to quickly post all saved photos and videos from your phone to Instagram.