Remaining 23:
Niokolo-Koba National Park
Sabratha
Aldabra Atoll
Timgad
Lake Malawi
Matobo Hills
Nanda Devi and Valley of Flowers
Khami Ruins
Cliff of Bandiagara
Rio Abiseo National Park
Kasbah of Algiers
Shark Bay
Thungyai-Huai Kha Khaeng
Island of Mozambique
Puerto-Princesa Subterranean River
Coro and its Port
Canaima National Park
Golden Mountains of Altai
Sukur
Lorentz National Park
Koguryo Tombs
Ruins of Loropéni
Socotra Archipelago

Thanks to Jarek for Niokolo-Koba National Park, Loropeni, Altai and Coro! He keeps sending more... Canaima as well.

And Puerto Princesa by Zos!

17 left:
Sabratha
Aldabra Atoll
Timgad
Lake Malawi
Matobo Hills
Nanda Devi and Valley of Flowers
Khami Ruins
Cliff of Bandiagara
Rio Abiseo National Park
Kasbah of Algiers
Shark Bay
Thungyai-Huai Kha Khaeng
Island of Mozambique
Sukur
Lorentz National Park
Koguryo Tombs
Socotra Archipelago

I can send some photos of Timgad and Kasbah of Algiers.

Yes please!

I'll send a few photos to choose from for Shark Bay.

elsslots

I have plenty of: Koguryo Tombs of course Tomb of King Tongmyong

but i have been to 3 others of which I have been inside of 2 and have photos. (cost me 100 euro per tomb though).
happy to share. sent me an email at chris@christravelblog.com
i will license them to you but strictly to you for free :-) sorry about that but it's also part of my living to sell them.

Thanks to Marcel, there are now 12 left:
Sabratha
Aldabra Atoll
Timgad
Lake Malawi
Nanda Devi and Valley of Flowers
Rio Abiseo National Park
Kasbah of Algiers
Thungyai-Huai Kha Khaeng
Island of Mozambique
Sukur
Lorentz National Park
Socotra Archipelago

Thanks to Roman Bruehwiler for sharing a photo of Heard Island!