If adding images on front side, still use heading with Bootstrap class of sr-only to add text so that screen readers will include it in list of headings.
Hover, Tap, or Tab to Flip the Card (CSS Only)
Card 1 Front
Card 1 Back
Card 2 Front
Card 2 Back
Card 3 Front
Card 3 Back
Click, Tap, or Tab+Enter to Flip the Card (Uses JS)