There is only one file type that uses the .T2B extension:
CyBook Thumbnail Image
Thumbnail image created by the CyBook black and white eBook reader device; stores a 2-bit grayscale image that supports four colors; generated automatically by the CyBook reader when viewing books; used for storing previews of book covers.
T2B files store a 96x144 pixel image using the four colors. The file format does not have a header or footer.
Updated: June 3, 2011