painting program to create pixel art and manipulate digital photos

 mtPaint is a free, open source graphic editing program which uses the GTK+
 toolkit.
 It is geared towards creating indexed palette images and pixel art.
 .
 Due to its efficient design it can run on older PC hardware (e.g. a 200MHz CPU
 and 32MB of RAM). It can edit indexed palette or 24 bit RGB images and offers
 basic painting and palette manipulation tools.
 .
 It is aimed to be simple and easy to use. it also can handle JPEG, GIF, TIFF,
 BMP, XPM, and XBM files.