Ideally Facebook wants an opengraph tag:
Open Graph Warnings That Should Be Fixed
Inferred Property: The 'og:url' property should be explicitly provided, even if a value can be inferred from other tags.
Inferred Property: The 'og:title' property should be explicitly provided, even if a value can be inferred from other tags.
Inferred Property: The 'og:image' property should be explicitly provided, even if a value can be inferred from other tags.
Would like each gallery page to include this information so the correct date is passed to Facebook - especially the og:image property pointing to the particular gallery image.