If you have something new, interesting or useful suggestion for Google plus, you can send your suggestion to Google Plus team. Google Plus team is open for new suggestion from users.
Google Plus also wants you to vote other feature requests suggested by other users. You can simple Like or Not like or Flag as inappropriate any suggestion.
You can vote or submit new feature requests at Google moderator. You will need to login using a Google account. Visit below link to submit or vote any suggestion.
[url]Google Plus Feature Requests[/url]