Profile pictures and providers issues

If a user never visited a SharePoint page before, his picture will never be retrieved from SharePoint provider
If a user never visited Outlook before, no profile pictures will be retrieved from Outlook provider to that user
If a user is not logged in (or with a valid cookie session) on Delve, no profile pictures will be displayed from the Delve provider

By using SharePoint provider, is possible display all the pictures (regardless being uploaded on Office365 or SharePoint profiles). So, the profile picture will be displayed to all users with one condition:
- condition - A user whose photo has been uploaded to Office365 and has never visited a SharePoint page, does not yet have his photo available in SharePoint, which means that his photo will not be shown to anyone

By using Outlook provider: with Outlook provider it is possible to show all profile pictures, even pictures of users who have never visited a SharePoint page before, but with an associated condition and restriction:
- condition - For the user to be able to see the profile pictures, he must at least have a tab with Outlook online open in his browser
- restriction - All the profile images must be uploaded on the Office365 profile (if they was uploaded on SharePoint profile the result may not be as expected)

By using Delve provider shows all the images regardless users have visited Outlook before, or not. The issue is the authentication token is not the same for SharePoint and those images only appear to users that are logged in on Delve.

All other providers can have similar results to the above mentioned, with the exclusion of Microsoft Graph.
Microsoft Graph is an API service that has no restrictions for users who have added their profile picture, regardless of the service where they have done so, as long as they belong to the organization.

Important: After all conditions and restrictions are solved is important to clear the browser cache to see all the pictures immediately.