Here are my flags sorted by their status. The list is incomplete, full list is merge of this and this page. You can see this list too.
Flags of countries
editState flags for state languages
editModified state flags for more-state languages or multilingual states
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Fijian (not best)
Combined flags for more-state languages
editFlags of non-cognate states (some may be disputed)
editFlags of country subdivisions
editFlags of official subdivisions
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Southern Altai (or here Krai?)
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Northern Altai (or here Rebublic?)
Flags of unofficial subdivisions
editFlags and emblems of cities
editEthnic and political flags
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Central Bicolano (not best)
Historical and proposed flags
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Ancient Greek (possible?)