Flinto - The prototyping tool designers have been waiting for.
PhotoFlare - Quick, simple but powerful Cross Platform image editor.
Base UI Sketch Framework - Huge set of everything you need to design and prototype
showFoto - ShowFoto is the standalone image editor of the digiKam project.
Glyphy - Copy & paste fancy fonts + cool symbols ☞✺✐™
PhotoDemon - Lightweight portable BSD licensed photo editor for Windows focused on performance and usability.