Need samples of big endian encoded tifs
The current ImageMagick can make them.  Given a little-endian TIFF,

convert le.tiff -endian msb -define tiff:endian=msb be.tiff


and vice versa:

convert be.tiff -endian lsb -define tiff:endian=lsb le.tiff


Run

identify -verbose be.tiff | grep ndian


to see what happened.