+ { wszTiffCompressionMethod, VT_UI1, VT_UI1, {.iVal=WICTiffCompressionDontCare} },
This .field=value initialization syntax is not acceptable for Wine (not in C89). I don't know another way to initialize unions.
+ if (clsid_encoder == &CLSID_WICTiffEncoder) + todo_wine test_specific_encoder_properties(options, testdata_tiff_props, all_props, cProperties2);
It might be better to mark the individual properties with a todo, so they can be added one at a time.