From the following IHG breakfast threads:
Tipping required with free IHG Diamond breakfast?
Major Holiday Inn Breakfast Devaluation
Kimpton Diamond Breakfast
Diamond Breakfast Amenity at Holiday Inn Club Vacations Properties
Diamond breakfast for two rooms
This one out of nostalgia: The IHG Breakfast Prices Thread

Comes here the case of Intercontinental New Orlèans.
As diamond, I was proactively offered complimentary breakfast and was issued 2 vouchers and a welcome letter.
Points of atttention concering the voucher:
1) voucher is valid for the member and his registered guest staying in the same room
2) choice - buffet
Or
- 1 main menu item
3) specialty drinks are excluded
4) unlimited non alcoholic beverages are included
Above is all according to the T&C
The whopper is that gratuities are not included.
As reported by one of the threads......

But wait, it gets better.......
Noteworthy and especially discussion worthy......
- breakfast buffet is subject to 20% service charge
As gratuities were excluded from the diamond welcome amenity: breakfast voucher ...... what's the $ determination in 20% service charge ?
- embedded in the small print: "breakfast has a capped dollar amount of $33 per person."
Which means the gratuity of 20% is at max derived from $33 = $6,60 for breakfast for 2 persons in 1 room.
I do hope the staff really get that amount.

And what are the breakfast possibilities at IC New Orléans and the $ pricing?
But.....if your stay doesn't include breafast,
+ 10,75 % sales tax
+ 20% service charge
So just you are aware .... somethings are less obvious than others.

PS: A Starbucks is around the corner if you are more a grab and go person.

EDIT2
I've asked 3 different staff at breakfast, diamond welcome amenity: breakfast voucher does cover gratuities completely and the breakfast team on duty will receive the $6.60 per voucher.