Now you can also keep attachments on participants.
To configure this functionality, you need to add an Attachment custom field to the Participant object.
To do so click on Setup.
Under Administer section expand Create options and choose Objects.
On the list of Precursive objects choose the Participant object.
In the Custom Fields & Relationships section click on the New button to create the Attachment custom field. It should be a Long Text Area field with an API name attachment__c
When the Attachment field is created, you can add it to the Participant layout. To do so, open the Custom Properties tab on the Admin page. Choose the Participant object from the drop down list and click Add.
Add a custom field with path: attachment__c and type Attachment.
Now everytime you will add a participant to a project Attachement field will be displayed on the participant modal and you will be able to add an attachment to a participant.