Ostentation (an excessively showy exhibition) can have these synonyms based on the context : pretentiousness, gaudiness, pomp, affectation, or garishness.
Ostentatious is when you show off. Here are some sentences.That outfit is pure ostentation; go put on something more suitable!Ostentation is a sign of a vain person.I paid no attention to the ostentation around me, but listened carefully to what was actually said.
frippery = ostentation
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a group of animals
A flock of peacocks and peahens is called a Party.
pretension, affectation
pomp, pomposity, splendor
It could be opulence or ostentation.
muster or ostentation
Because they disagreed with the ostentation of luxury shown by the church
The collective nouns for peacock are a muster of peacocks or an ostentation of peacocks.
If you mean group name as in collective nouns, then muster, ostentation or pride