I’m trying to use a metaphor along the lines of
Blank canvas roughly fits some of the above, but it’s very common. Are there any other metaphors that similarly fit the criteria?
"Tabula rasa" is almost an exact translation of "blank canvas" and has a similar meaning. However, it might not fit the rest of what you want. (For example, it doesn't mean "something multifaceted". In fact, "multifaceted" is nearly an antonym of "blank", so that aspect of your question confused me a bit.)
This could be described as a new frontier, which very well captures the notion of something unexplored that holds great possibility. It also happens to be a term used in a 1960 speech by John F. Kennedy, describing the many aspects of promise and peril in the coming decade, from scientific to social to political, which gives it an additional connotation of multifaceted-ness that you're looking for.
"Uncharted territory" or "uncharted waters".
Uncharted refers to something not recorded on a map. Uncharted waters or uncharted territory can refer literally to places not yet explored, but it can also be used figuratively to refer to unfamiliar situations in general.
I'll pick up on the serious objection that has already been made to this question (user MarcinMahattan), and I'll take the opposite view that the OP is rather deficient as regards its title and that the real quest is not expressed in the title but in the body of the post, the title being in need of a modification. Accordigly, I propose the term "fresh territories", which references show to be usable figuratively.
(ref.) Their assumptions and the language used to express them are still heroic , although one has a sense at this point of brilliant new singers carrying the old poetical equipment into fresh territories
"Untapped potential" seems to fit your desired meaning including "ripe for exploration" and "full of possibilities"
Example usage from the above Cambridge dictionary link
To be fair, some of the larger companies have made substantial moves in that direction recently, but there remains untapped potential.
Or even just "untapped" stands on its own fairly well depending on your usage
If a supply of something valuable is untapped, it is not yet used or taken advantage of
In the above case the "something valuable" is the potential, but you could have "untapped territory" or "untapped resources" etc.
Virgin; blue skies; verdant pastures (biblical: Ezek 34:14).
How about something like "potter's clay", "wet clay" or "fresh clay"? The idea being that this is a lump of material with the potential to be moulded and sculpted into anything.
The way you describe it seems to fit the expression uncut gem, or alternatively diamond in the rough. A rough diamond or other gem stone has potential, but it needs to be cut (which can be done in a variety of ways) to reveal its beauty and value. A cut diamond is obviously multi-faceted, but it has all kinds of applications, such as drill bits and record player needles, so it's multi-faceted in its use too.
The desired tone is unspecified (e.g., technical, formal, poetic, colloquial)... These might also apply: "clean slate", "new horizon(s)", "virgin territory", "open field", "spring of possibilities", "untapped well", "bucket to be filled", "banquet table"... "bag of cats" ;-).
Personally I like "an unwritten page".
