Gamify the platform more. A large portion of the userbase is gamers.

Functionally, users engage better when they have objectives and rewards. Currently the backend has an achievement system for streamers to allow them to have benchmark goals to reach for their stream.

So to capitalize on that, expanding the Drops & Rewards to include Achievements for both users and Streamers. Currently Streamer metrics are what the driving force behind available streamer achievements.

This entire system would need rewards to be a driving force for users to engage with. Emotes, badges, nameplates, titles, profile pic frames, platform themes. This is a double-header here, as some of these functionalities do not exist.

So what can a viewer achieve?
Used Channel Redemption, Use X Channel Redemptions, Used Bits, Subscribed, Subscribed for a streak (on any single channel), Anniversaries (yearly), Sent first message, sent X messages (anti-spam delay on counting) used an emote in a message (anti-spam delay on counting), used X emotes in messages, participated in a poll, participated in X polls, accrued X channel points (final achieve at 1 million in a single channel), watched a stream together stream, watched X stream together streams, watched a recommended stream for 10 minutes, watched a recommended stream for 24 hours total time, participated in a raid, participated in x raids, follow your first channel, follow 5/10 channels, gift a sub, gift X subs, used a powerup, used x powerups, reach a watch streak of x in any channel, watched a Twitch stream, browsed the carousel on the front page, watched a stream in just chatting/DJs/Art/Music category, watched a clip, watched x clips, created a clip, created x clips, shared a clip, shared 5/10 clips, watched a story, used the mobile app, received a drop, earned an emote from a promotional event...

And the list goes on. All of these are micro-incentives for users to engage and learn the platform. As users learn the platform more through some of these, they are incentivized to engage in it with further achievements and stretch goal achievements. A similar list could be added for streamers themselves, as the platform is a 2-part equation. Rewarding both sides for both providing and engaging both. Streamer-based achievements would be equally about feature engagement, both introductive and sustained engagement.

As for new rewards, back to the other end of the equation. Emotes and badges are already a way for the users to have a modicum of identity. We need more. So light touches on the user-end, primarily cosmetic.

Nameplates - A rarer cosmetic, a backer to your name in chat, your profile when viewed (when panel is displayed by clicking your name), and when featured in a stream-together title or @. The in-chat display of the nameplate would be a per-channel toggle, so streamers can turn them off for user-friendly engagement, but also may be toggled off from user-end for similar reasons.

Profile Pic frames - Currently a highlighted feature best in example on Discord. A simple frame for your icon that would display in your profile (or popup when clicked in chat), would appear in the left shelf for recommended and the top right display of your icon on-site. A small visual frame to fit around your image.

Platform Themes - We have dark mode, we have light mode. Some various unlockable gradients and other visuals for backgrounds or channel pages on native Twitch. Simple patterns, flat colors and patterns to not obscure features.

Emote Shelf Expansion - Currently posted another idea involving having a shelf for users to select from their available emotes, this idea would go hand-in-hand with that idea, giving them extra shelves or space on those shelves in the emote selection window.

Now how distribution would work? Well, certain achievements would unlock very specific things. For example Twitch's Bleed Purple, a staple of it's branding is the purple. So for a sort of site-pride engaging achieve, you might unlock a light Glitch logo (Twitch's site symbol) as a repeating pattern for a background.

For the rest of everything however, achievements would award points of varying amounts for redemption in a basic shop. These offerings would be basic background colors/gradients, old offered emotes from promotions, simple frames, etc.

To extend the shop however, Twitch can and should create a monetized front for that. If this occurs, I would recommend the focus on creators and artists, allowing users to submit, get approved and gain a profit when their item is sold. (It wouldn't be a free-for-all, just a strict entry/approval process and rotating offerings.) For a similar market example, see Warframe's Tennogen. (Regional offerings and exclusions obviously may apply, free achievement point shop would be global though.)

This dual-front draws attention to all Twitch's current features and allows another monetization method for Twitch. The entire system being just a way for Twitch users to drive engagement and thereby improve quality of the site/service. By gamifying the experience, users may hopefully feel encouraged to engage more and through those engagements, more positively.