IIMG is a type of file also known as an "Interleaf image". Such files most likely contain images that were created and/or edited using software programs created by Interleaf, an American IT developer which produced graphics editing tools for the publishing industry throughout the 1980s and 1990s. The brand was acquired by Broadvision in 2000. The IIMG format is currently considered rare and obsolete.
The quick and simple way to handle your files is to get a quality piece of software, such as reaConverter. This software is extremely efficient in managing a wide range of batch conversions. As you will soon realize, reaConverter will help you avoid spending countless hours trying to figure out how to convert multiple IIMG files as once.
JPEG JPG PNG GIF TIFF TIF BMP ICO EMF WMF AI PDF EPS PS EPI WEBP WEBPLL JP2 PCX TGA DWG DWF DXF DGN WMZ CGM DRW SHP GBR PCT MIF PLT PCL SVG WPG CIN DCX DIS HRU MTV PRC RAD PIC RLA QRT SGI XBM XPM SWF CAL FAX FITS PSD PGM JXR BPG APNG DDS SVGZ CG4 FLIF AVIF