A note from the author of RayLab:

The textures blob.iff and flowr256.iff were created by Harold Poskanzer,
who generously allowed me to include them in the RayLab distribution.

The originals and many more, which are all 24-bit, can be found at:
http://www.best.com/~drzeus/Art/Textures/Textures.html

I like them very much, and they make great textures, don't you think?
Unfortunately they would have taken up too much space when stored with
the IFF24 format, so I could not include them all.