Did you already include Stardew Valley? The Dev has done a lot of work on it since release, including several free content additions. And due to the success of the game, it looks like they'll keep working on it for the foreseeable future.

I love the Stardew Valley and the dev surely put a lot of work into the game and into the updates. But for now I don't really see additional content. Most of the updates seem to be adjustments of what was already included. I will surely include the game once the big pdate (Version 1.1) comes out..

But please tell me if I missed something and there was indeed some extra gameplay content by now.

You'll be able to include it for sure once it gets multiplayer.

He also announced new events, new farm buildings, new crops and additional marriage candidates. That should be more than enough to put it on the list.

On February 11th, 2015, Seven Kingdoms 2 was upgraded to <span class="bold">Seven Kingdoms 2 HD</span>. The owners of the original version got the HD version for free, but the game's price was increased from $5.99 to $9.99. The old version is still available as an extra.

Thank you. I will add it to the mix.

Seven Kingdoms 2 HD and GALAK-Z have been added to the GOGmix. I've also edited the entry for Ashes of the Singularity (the DLC isn't free any longer).

http://www.gog.com/mix/games_that_got_addtional_content_for_free_after_release

The original version of the first Broken Sword was added as an extra for free to Broken Sword: Director's Cut on January 11th, 2011. The price remained the same.

Broken Sword 2: The Smoking Mirror was upgraded to Broken Sword 2: The Smoking Mirror Remastered on May 31st, 2011. Owners of the original version got the upgrade for free, the price remained the same and the original version is available as an extra for everyone.

Pro Pinball Timeshock originally launched only with its DOS version, but had its Windows version added for free on November 19th, 2013. The price remained the same and both versions are available from one installer via separate shortcuts.

Thank you. I could have sworn that I've added the Broken Sword games a long time ago, but it seems I've missed them somehow.

I've added the three games to the GOGmix.

Darkest Dungeon got a new patch that introduced town events. The game has been added to the GOGmix.

http://www.gog.com/mix/games_that_got_addtional_content_for_free_after_release

8-Bit Armies got a free DLC and has been added to the list.

Oxenfree just got a free content update.

Oxenfree was added to the GOGmix.

https://www.gog.com/mix/games_that_got_addtional_content_for_free_after_release

Thank you for reporting. Ziggurat was added to the GOGmix.