The introductory glyphs for each period do resemble each other but with lots of variations. (I have excluded the introductory glyph for the 9th period with its unusual 'toki'.)

I think we can see that the first 4 periods (top) are different from the second 4 periods (bottom). The first 4 seem to have double 'tokis', the second 4 only one 'toki' each. (Remember that the hand inwards in the 3rd period is equivalent to a 'toki'!)

The 5th person has an elbow adornment we can recognize.

The last person has only one ear, a sign which certainly has a meaning. If we regard the 'ears' as eyes, than we could say that in the 8th period light is disappearing. The elbow adornment also signals 'finished' or 'closed'.

The light sign in the 7th period is but small and without the usual 'eye'.