PhotoDemon - Lightweight portable BSD licensed photo editor for Windows focused on performance and usability.
RealWorld Paint - RealWorld Paint is an free portable image/photo/animation editor.
PhotoFlare - Quick, simple but powerful Cross Platform image editor.
JugiPaint - JugiPaint is a painting software with diverse tools for various types of illustration work.
PixBuilder - Free Photo Editing Software for PC
Paint +++ - Paint +++ is a native image editor for Mac that enables you to complete everyday image editing tasks in a single place.