Rather than start a new topic, I am reviving this thread as I can't see that it has been resolved.
I have a similar issue - I have collected data on the phone and uploaded it to Google Sheets. This appeared to be a really useful way of collating data from a small team rather than using Aggregate or Central (I am notoriously useless at installing and configuring the server!)
However, when I download the spreadsheet I only have a hyperlink, which does not allow me to access the images directly, or the image names. I have found that the images are stored in a separate folder and have the 'full path' from my phone as their name i.e. storage_emulated_0_odk_instances_[instance_name]_[image_name]. This makes it hard to integrate with data imported from Briefcase (where the cell contents refer to the image name and relative path, e.g. media/[image_name]). However I can batch rename them to remove the full path...
I have tried using the google sheets script mentioned above but this doesn't appear to give me access to the image name (maybe it's not even intended to do so now I study the script itself!).
Essentially I want to be able to use my data offline, so exporting to excel / csv (with image name column that matches the downloaded images). I can then visualise / analyse the data locally when I have no internet connection (common). I think this is the same as @Souligno but I can't see a solution here or on the related thread.
While I'm at it, it would be really useful for Google Sheets to store location data in the same format as Briefcase exports it - again merging data is more of a hassle than I expected... Sheets uses one column Y,X (a Google convention or just Lat, Long?) whereas Briefcase exports 2 columns [field]-Latitude and [field]-longitude.
Many thanks