Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
Pixel Art Studio - A purpose-built drawing tool for pixel artists
Batch Image Resizer - Resize, crop, shrink, flip, exif-rotate, convert, enhance, process multiple pictures and photos with professional software! 120+ Actions, 30+ Image Formats
Pixilart - A drawing app for delightfully retro pixel art
DVDVideoSoft Image Convert and Resize - Free Image Convert and Resize is a compact yet powerful program for batch mode image processing.