Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
Grafx2 - GrafX2 is a bitmap paint program inspired by the Amiga programs Deluxe Paint and Brilliance.
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
Piskel - Piskel is a website where designers online create sprites or pixel art.
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.