Comparing images between versions of Tableau Server is a great way to find issues prior to upgrading your production instance. However, small visual differences between versions are fairly common, and add noise to the results of the image comparison process that aren't necessarily of concern. Adding a feature by which sheet / dashboard summary data is compared between servers would allow for more precise comparisons that are likely more concerning.
Comparing images between versions of Tableau Server is a great way to find issues prior to upgrading your production instance. However, small visual differences between versions are fairly common, and add noise to the results of the image comparison process that aren't necessarily of concern. Adding a feature by which sheet / dashboard summary data is compared between servers would allow for more precise comparisons that are likely more concerning.