Unused Steam Codes

Define while. Weeks/months they are fine or you can request new one. Multiple years ins some cases might be worse.

These groups:

Delete giveaway if key is not working
Lootboy SG

or these threads:

Invite-only Giveaways
Anti-Ninja Key Drop

I would recommend the 1st one :)

You can paste them in JPG format (I think this avoid bots) our doing some "math" accounts (like ** = 2)

Are there so many games like this for you to worry? :-O

Why not just make a bunch of invite only giveaways, and link them as a train, then post the start here in the forum?

Or just post a list of invite only giveaways.

That 's what most people do with extra bundle keys

Dunno about the drama you speak of, but alot of people also just drop a comment with a llnk to an invite only giveaway, at the end of these most popular threads...

https://www.steamgifts.com/discussion/tnWVh/anti-ninjas-key-drops-no-keys-in-messages-though/search?page=last
https://www.steamgifts.com/discussion/Rl7Jo/dont-like-bots-post-your-random-invite-only-giveaways-here/search?page=last
https://www.steamgifts.com/discussion/glfql/community-word-game/search?page=last
https://www.steamgifts.com/discussion/t3RIy/the-perpetual-i-need-5-entries-for-a-giveaway-thread/search?page=last
https://www.steamgifts.com/discussion/hK2kQ/orphan-keys-drop-thread/search?page=last
https://www.steamgifts.com/discussion/zI06z/flash-quick-giveaways-you-snooze-you-loose-also-feel-free-to-add-some-if-you-also-want-to/search?page=last

Another popular method is to make a puzzle on jigidi.com or quiz on 2solve.me or utilize a more abstract obfuscation of the 5 character string which is unique to each giveaway..
https://www.steamgifts.com/discussion/TLR8m/zelgh-magic-guide-to-basic-sg-puzzling-update-october-2017

Start with your friends wishlists. See who might want what you've got.