Polycount within iClone is fixed and cannot be changed. You could export the character and reduce the polys, but it would no longer be a standard iClone character. You would have to re-rig it probably and then import back as a non-standard character.

For crowds, where details are often less important, you could use low-poly characters, which are available in the MarketPlace.

EDIT: I try to get rid of the light-blue background, but I can't...

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