Alternatively, you could compare image checksums before and after moving them into postgres. The advantage is that you don't need to export or view any file, and you compare globally all your images. If the checksums are identical, the data are identical. On the MSSQL side, checksums can be computed with hashbytes() as suggested in this stackoverflow answer: [3] On the postgres side, use functions like md5() or sha256() directly on the bytea column.
This is what I did when migrating Oracle xLOB columns to bytea. Had to use upper(md5()).
I didn't suggest this earlier, since I don't know the details of MSSQL's Image data type.
