You won't get pictures of every engagement simply because they don't release them of things like 'meetings' or 'receiveds'.
Who would be interested in seeing a group of people sitting around a table talking about something - once or twice yes but 100s of them - no. All royals do a number of these of things.
The 'out of palace' engagements are the ones where photos would be possible.
Not even all the receptions a royal attends have photos released.
A full copy of the CC from 1981 to her leaving the royal family when her official engagements would have stopped being recorded is the only way to do a full count and the online CC only goes back to 1997.
When I retire I intend on visiting a few places where I know they had the CC going back to the beginning on micro-fiche to find out if they digitised the entire copies of The Times or whether they only did selected bits. If they digitised it then I will attempt to do a full count for Diana - along with the rest of the BRF since WWII.