[Note: The answer is from the mainstream Salafi perspective (cause the OP asked for it)]
OP asked: From the Salafi perspective, is the prohibition of depictions of humans and animals retrospective?
Yes. According to this IslamQA fatawa (IslamQA is one of the most respected source of mainstream salafi doctrine), it is obligatory to destroy idols. It states:
The evidence of sharee’ah indicates that it is obligatory to destroy
idols, for example:
1 – Muslim (969) narrated that Abu’l-Hayaaj al-Asadi said: ‘Ali ibn
Abi Taalib said to me: “Shall I not send you with the same
instructions as the Messenger of Allaah (peace and blessings of Allaah
be upon him) sent me? ‘Do not leave any image without defacing it or
any built-up grave without leveling it.’”
2 – Muslim (832) narrated from ‘Urwah ibn ‘Abasah that he said to the
Prophet (peace and blessings of Allaah be upon him): “With what were
you sent?” He said, “I was sent to uphold the ties of kinship, to
break the idols, and so that Allaah would be worshipped alone with no
partner or associate.”