Thanks everyone.
While asking of the forum group had also sent a help message into Geocaching HQ, response - "At this time we don't offer that functionality, but I agree that it would be useful. We appreciate that you took the time to let us know your feedback, and I've passed it on to our developers and designers."
Seems to me to be (in my innocent non technical view) a fairly easy sub routine script to add to the trackable page. Alongside where it has 'Upload Photo' have another button which opens up your galley page. Click on the appropriate photo to be selected which closes the galley page and creates a link to the file name of the photo. Hay presto photo added (linked to) to log entry. But not being a programmer / code writer I guess it'll be more difficult than that.
Happy Geocaching everyone and stay safe on the trails.