Made my GoGmix with games, which potentially (e.g - engine, they are built on, has such feature out of box with no way to remove it. or its described in their EULA and such) may collect and send some information from your pcs. Its very wip, but, if there will be interest, I ll expand it soon:
gog.com/mix/games_w_potentially_telemetry

Also there will be info about how to avoid that, if possible (for example - some games have ability to turn telemetry off in settings, but its rare, sadly)

Okay, here's mine:

Every roguelike I could find!
10 games based on comics
Be an octopus/hacker/queen/pig/badger/vampire/thief ...
Lure of the Box Art Babes
Games without a monotary system
Games where in-game currency is actually useful or fun
Games in Underwater Environment
7 deadly sins. 7 games to play.
50+ games: A Chronology of Human History
S E X in video games

You just want 10 games? Because there are many more which are based on comics (e.g. The Wolf Among Us, XIII or the Batman Lego game).

Yeah, that mix has fallen a bit behind. Good catch!

He might have a hard time adding that one to his mix...

I wasn't sure, if it's possible to add removed games to GOGmixes. It seems it is not.

Great idea for a mix! However, maybe you should use one of the game descriptions to write a bit about telemetry itself and whether it is something worth bothering about. (I know nothing whatsoever about it myself)

Problem is that there is way much to say, to keep it inside twitter-sized reviews. Im tries to write reasons, why I include this or that stuff, but thats it. Hope, GoG will improve their mixes soon, since their "modern electron-powered Galaxy client" exist. I really love, how it works in steam, for example. E.g - you can describe your curator and discuss every curation with community, which helps drammaticaly - without feedback, Im sometimes not sure - should I include X title, or not (like recently happend with Tales of Maj'Eyal, which shouldnt collect anything, except characters data and chat logs (and only if you will register account on their site) but establishes online connection with dev's server ever if you will disable all online features). Yeah, I still can add people, who wanna chat about it, inside my friend list, but its not that good for this.

Does anybody know, if we already have a mix for "Games within a game"? Stuff like Day of the Tentacle that includes Maniac Mansion, Night in the Woods that includes Demontower or Might and Magic VII that includes Arcomage.

Not really the season but still:
I created a GOGmix featuring games that have X-Mas levels or mods.
GOG Games with X-Mas Levels or Mods
(Disclaimer: It's my affiliate link.)

There's a mix for "GOG games that include bonus games" (it's called something very close to that); I think it's maintained by Treasure. At any rate, it's got its own forum topic, and I know people had therein suggested games like DotT and The Bard's Tale (2004) for inclusion. EDIT: But I don't think it limited itself solely to games that can only be played from within another game.
RE-EDIT: The list I was thinking of is here, but is maintained by kbnrylaec, not Treasure, and seems to be only a forum thread (no associated GOGMix as of yet).
TYPOGRAPHIC EDIT: Good god, how out of it was I when I wrote this? -_-

Because I was in the mood I started a GOGmix with games that have bunnies today! I'm pretty sure I'm still missing some GOG games, especially adventures, but so far it has been a lot of fun! :D
GOG Games with bunnies
(Disclaimer: Again with affiliate link.)