Your description suggests the 'Automatically resize to fit contents' setting hasn't been (un)applied consistently or that you're using some process you haven't mentioned to insert the images. Assuming the documents being created from a template and the images are being inserted manually:
(a) the table must already exist in the template, or have those settings applied when the table gets created (there are no Word defaults you can change for the 'Automatically resize to fit contents' or row height options); and
(b) the image must be inserted into the table.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]