英文)問一句句子結構

Herculaneum was another city buried in the ground when the volcano Vesuvius erupted. Most tourists only know about Pompeii and Herculaneum is unheard of by most people.

Let me simplify the sentence for illustration purpose.
Herculaneum is showing off its glories, including some (artifacts) never before seen by the public.

The second part of the sentence can be written in a relative clause like this:
Herculaneum is showing (verb) off its glories, including some artifacts that/which have never been seen (verb) by the public before.
Note that the relative clause has a verb.

A relative clause can be replaced by a present or past participle, depending on the structure of the clause the participle replaces.
Herculaneum is showing (verb) off its glories, including some artifacts never seen (past participle) by the public before.

including some never before seen by the public
這句句子中沒有一個main verb

Main verb 是不需要的因為這不是一個 clause(分句)。verb 以經被 past participle 代替。

including some never have been seen by the public before
會唔會好些- -?
No, this is wrong. 用 verb 就必須用 that/which relative clause.

同埋其實including some never before seen by the public
呢句本身結構有無問題

無問題

The second part of your question is related to "Never before". Putting never before in front of the participle is to emphasize the fact that it is the first time the artifacts are shown to the public.
Example:
Never before were the artifacts seen by the public.