Hi kbeach,
According to your post, I have understood that you want to upload multiple photos to SharePoint Online site.
If this is the case, I suggest you use Microsoft Document Connection to achieve it, here are the steps for your reference:
1.In Finder, under Applications, open Microsoft Document Connection.
2.On the Document Connection menu, click Preferences.
3.In the Preferences window, make sure that the Enable Basic Authentication check box is selected and then close the Preferences window.
4.In the main window, click Add Location, and then click Connect to a SharePoint Site.
5.In the Address box, type the address for your team site.
6.Click Connect.
7.In the User name box, type your full Microsoft Online Services ID, like someone@contoso.onmicrosoft.com.
8.Type your password and then click Connect.
After you’ve configured Office with Document Connection, you can save files directly to your team site from the Office desktop applications.
Thanks,
Eben Liu