To get the images from a Facebook page using the Graph API you will need to do the following steps.
Authenticate you application with the 'manage_pages' permission. https://developers.facebook.com/docs/facebook-login/permissions/v2.3#reference-manage_pages
Once you get a user access token for your application with this permission make the call Graph API call /me/accounts and retrieve the Page Access Token for your page.
Once you have the page access token you can use the Graph API as you are that specific page.
The following is a breakdown of all the edges you can use with your page access to
https://developers.facebook.com/docs/graph-api/reference/page
In your instance you will most likely want to be using the {page-id}/photos endpoint with this access token which will allow you to retrieve photos from your page.