TIFF image format is not something DFDL v1.0 can describe.
Nevertheless we need an approach that illustrates how to deal with it.
I think this means a preprocessing program, and then a DFDL schema to turn the result of the preprocessor into an Infoset. For unparsing, a post-processor also.
The right approach remains to be seen, but we need to show how to deal with TIFF.