Here is a suggestion for several new Great Wonders for consideration.

Sphinx Force peace treaty (at no cost) with any Country currently at war
Ancient Era (Great Engineer) (2x Great Person Points per turn), +1 ☺, +6 Culture
Available after discovery of Sculpture Tech
Build faster 50% with Stone, -10% War Weariness
Change game classification of Sphinx as Stonehenge replacement as Sphinx
was more aesthetic/work of art/political effect than Stonehenge
World Epic +2 Science, +1 Culture to all Story Teller Circles, +1 free Great Artist
Ancient Era (Great Artist) (2x Great Person Points per turn)
Available after Story Teller Circle built in City
Represents epic story of the flood found in many civilizations
Tower of Babel Receive 2x free Settlers
Ancient Era (Great Engineer) (2x Great Person Points per turn)
Available after discovery of Stone Cutting Tech
Simulates the first diaspora of humanity after the Great Flood
Code of Hammurabi +1 ☺, +4 Culture, +1 $
Ancient Era (Great Merchant)(2x Great Person Points per turn)
Available after discovery of Writing Tech
May be built by Great Scientist
First code of laws (presumption of innocence/minimum
Circus Maximus +1 ☺, +6 Culture, +1 ☺ each 20%, Available (same as Colosseum)
Classical Era (Great Engineer) (2x Great Person Points per turn)
Requires Hippodrome (a new building) in City to build
Circus Maximus was built before Colosseum and held over 100,000
Build faster 50% with Marble and 50% with Masonry Materials
Diocletian Baths +2 ☺, +2 Health, +2 Culture, Requires Aqueduct in City to build
Classical Era (Great Engineer) (2x Great Person Points per turn)
Available after discovery of Water Pump Tech
Build faster 50% with Marble
Largest Roman bath - occupied 32 acres and held 3000 bathers
(Delete Great Wonder Mohenjo Daro bath – too small not Great Wonder stature)
Great Cothon of Carthage +1 Food each water tile worked, +2 Production Points for naval units each turn
Classical Era (Great Merchant) Famous artificial harbor built by Carthage, +2 Trade Routes in City
Available after discovery of Shipbuilding Tech
+4 Experience Points each naval unit built in City, Expires at start of Renaissance Era
Shaolin Monastery +1 free Spy Specialist in City, +4 Culture, +5% City Defense
Medieval Era (Great Spy) (2x Great Person Points per turn)
Available after Monastery is built in City, Spy limit increased by two
Spies spread culture in other Countries additional +20% chance
May be built by Great Prophet
State religion must be Buddhism/Taoism build/operate
Order of Assassins +2 free Spy Specialists in City, -2 relations with other Countries
Medieval Era (Great Spy) (2x Great Person Points per turn)
Available after discovery of Divine Right Tech, May be built by Great Spy
Spy limit increased by three, Expires after discovery of
Spies may attempt to assassinate foreign leaders causing civil
disorder (+10% chance success over chance to cause revolt)
Grand Bazaar of Istanbul +1 ☺, +4 Culture, +2 Trade Routes, +1 free Merchant Specialist in City
Renaissance Era (Great Merchant) (2x Great Person Points per turn)
Available after discovery of Market Tech
May be built by Great Merchant
Requires Market in City to build (and 4x total Markets)
Grand Bazaar was and continues to be incredible tourist attraction
Medici Bank of Florence +35% $, all Banks get +5% $, +1 free Merchant Specialist in City
Renaissance Era (Great Merchant) (2x Great Person Points per turn)
Available after discovery of Double Entry Accounting Tech
May be built by Great Merchant
Medici Bank was first major bank in western civilization-very important
Bolshoi Ballet +1 ☺, +1 in Culture in City, +1 free Artist Specialist in City
Enlightenment Era (Great Artist) (2x Great Person Points per turn)
Available after discovery of Civil Liberties Tech
May be built by Great Artist
Requires Theater in City to build (and 4x total Theaters)
La Scala Opera House +1 ☺, +10% Culture in City, +1 free Artist Specialist in City
Enlightenment Era (Great Artist)(2x Great Person Points per turn)
Available after discovery of Opera Tech
May be built by Great Artist
Build faster 50% with Marble
Requires Opera in City to build (and 4x total Operas)
German General Staff -25% War Weariness, +15 free units, +25% Great General
Industrial Era (Great Engineer) (2x Great Person Points per turn)
All units built in all Cities receive +2 Experience Points
Available after discovery of Military Science Tech
May be built by Great General
Receive free Great General in City
MIT +50% Science, +2 Culture, +2 free Engineer Specialists in City
Industrial Era (Great Scientist) (2x Great Person Points per turn)
Available after discovery of Steam Engine Tech
Academic home of world renowned scholar Noam Chomsky
Build Laboratories 10% faster
Overall highest ranking technology institute in world

I like a lot of these suggestions. Namely, Circus Maximus and Shaolin Monastery sound pretty interesting. I hope some of these end up being implemented.