DA's Picture
[Freeware] Formerly commercial package for OS 3.5 and above.
David Pilling
Includes TWAIN drivers, and ImageMaster, an image editing program. Both are commercial software.
Mksprite
Makes pretty optimal sprite files from draw and Euclid files.
PD by Jochen Lueg
Includes FSIBatch, a utility which uses ChangeFSI to convert several images at once, in a batch job.
Sfmerge
Very simple utility that merges several sprite files into one.
SpriteClean
Designed to clean up random specks from scanned images, but will also automatically crop.
Variations
Applies a range of changes, to a greater and lesser extent, to an image, showing 9 possible outcomes.
Widget5
Image-processing package that supports 256 grey level (8bit), 65536 grey level (16bit) and 16.7 million colour (24bit) images.