Learn Italian: Questa sciarpa non è antiquata. Al contrario, è molto eccentrica! - This scarf is not outdated. On the contrary, it is very eccentric!

Al contrario (on the contrary) is a strong connector of contrast. It doesn't just introduce a different idea; it directly contradicts the negative statement before it (non è antiquata). It feels much more emphatic than ma or invece, stressing that the exact opposite of being old-fashioned is true.

Could I use the other contrast word from this lesson, bensì, here?

Yes, but you would need to change the punctuation. Bensì (but rather) is used to correct a negative statement within the same sentence. You would have to write: Questa sciarpa non è antiquata, bensì è molto eccentrica! You generally cannot start a brand new sentence with bensì.

Does antiquata mean the scarf is a valuable "antique"?

No, antiquata is a bit of a false friend here. It means "outdated" or "old-fashioned" and usually carries a negative connotation. If you wanted to say the scarf is a valuable antique, you would use the adjective antica (ancient/antique) or refer to it as un pezzo d'antiquariato.

Why isn't there a pronoun like essa before è molto eccentrica?