If you want Security Center users to see the picture of other users in Sipelia™, you must manually add them in the security settings of the associated custom field.
When created, the Sipelia™ plugin role automatically adds the Photo custom field in Security Center. The picture of each user, shown in the list of contacts for example, is provided by this custom field. To be able to see the pictures, users must be added to the Security property of the custom field.