The visibility of the Photos tab used to be settable in Application Settings, but Facebook changed the Application Settings page to only show third party applications and not those provided by Facebook, such as Photos. As a result there is no longer any setting to change this.
Facebook lists this as a known issue:
My Photos tab and albums are set to "Everyone," but people who are not my friends are not able to see my photos.
Despite choosing the Everyone privacy setting, some people's photo albums are currently not visible to non-friends. We are aware of this issue and hope to resolve it soon.
In the meantime, note that you can still share albums through the "public link". If you would like to submit a report, please click here.