How do I style this dress?

This dress has been sitting in my closet for years, and I have no idea what to do with it. It belonged to my grandmother, but I’ve never actually worn it out. It feels too dressed up for casual but not quite formal, either.

Is this actually flattering?
Where would you wear something like this?
How would you style it?
Would you keep it given the sentimental value, or is it just taking up space?