I just deleted 19k hi-res images from a table column and have a few questions about shrinking
If the goal is to make backups smaller, shrinking the data file(s) will not help accomplish that goal in this case, because all of those pages that were holding that max data were LOB pages that should be deallocated (potentially requiring a rebuild). 

So unless your drive is literally out of space, I don't see any reason to shrink the file from 8GB, unless you are 100% confident it will never grow that size again.

Note that when you shrink a data file you might actually increase fragmentation which could decrease read performance, impact memory usage, and reduce concurrency. The knee-jerk reaction there is to rebuild indexes, which fixes the fragmentation but increases the file size to make room for the new copies of the index. When the rebuild is done, those pages are freed up, but the data file doesn't magically shrink again, so you're back where you started, and have gained nothing.

If you delete 95% of the data, the backup size will go down, whether you shrink the MDF file(s) or not. An MDF file is just a container; its size does not affect the backup. The actual data affects the backup. More precisely, the number of pages allocated with any data affects the backup (which is why a table rebuild after a big delete might yield a difference in backup size).

This is easy to test for yourself, but keep in mind the impact you observe will depend on a lot of things, including data types, fragmentation, free space, and a host of other variables. Just look at the size of a full backup after each of these steps:


before you set the values to NULL.
after you set the values to NULL (and after dropping the column, maybe).
after rebuilding the table. 
after shrinking the database.


My theory is that, in almost all cases I can think of, there will be no tangible difference between the backup size after 3. and after 4. 

A different variable you might care about is the time it takes to restore that backup on another system, which will be dependent on the size of the MDF file(s) only in the following cases:


Instant file initialization is not enabled
The destination drive can not accommodate the current size


The first one is easy to fix, this is just a right you can grant to the service account. The second one should be easy to fix too: add disk space. There's no reason to sacrifice your primary system because your secondary system is inadequate.