I'll go first - my favorite post-launch tactic to continue a drumbeat of marketing is to gather and tell customer stories. Hopefully pre-launch you've had a rich beta where you gathered great customer stories, but certainly post launch is the time to talk to customers using the product in the real world.
On customer calls, PMs, designers, and engineers are going to be listening to users to understand what features to build next and how to create a better workflow for the user. PMMs should be listening for the value the product/feature brings. Does it save time? money? decrease risk? Gather these stories and tell them often.
It doesn't need to be packaged as a formal case study. Other avenues are:
- sales cheat sheets (example238) for reps to know and tell the stories often
- presentations/pitch decks
- social posts
- customer interview blogs
- customer guest blogs
- customer video interview videos
- on stage at a user conference (even better to have the customer on stage to tell their own story)