ah... i think amiga images are IFF
Actually, like .AVI's, .IFF are just a container format and can be anything. IFF is short for Interchange File Format
Most common Amige images are IFF-ILBM (compressed images)
But you'll also have:
IFF-ACBM (uncompressed images)
IFF-SMUS (tracked music)
IFF-8SVX (wave files)
And at least a dozen or so other subformats, for storing anything from word processor data to sound and images.
'IFF' isn't automatically an image file.