If you are a company administrator, you can enable the use of image library for the entire account. Both "author photo per slide" and "image branding" need to be enabled.
- Select Administration
- Select the Presentation Settings link
- Select the Yes radio box option for Author per slide
- Select Submit
- Now select the 'Viewer Options' link
- Under Image Branding, select yes for 'Allow authors to override Author photo'
- Select Submit.