I've had a "home lab server" for a while now, it's nothing special but I think I can do more with it, I just don't know what to do with it... I currently use it just for a pihole and (sometimes) a Minecraft server or a web server... I used to also have a nexcloud and a searxng instance (which I will probably bring back)... Any ideas for other things I can run on it?
That's a really open-ended question. Depends purely upon your interests and appetite for risk, etc.
Might be worth looking at, from a Docker perspective:
AdGuard Home (I think it's better than Pi-Hole)
Wireguard or similar. Great for reaching your services when away from home.
Audiobookshelf. Audiobooks. There are good apps.
Calibre-Web. Ebooks.
RSS feed reader, for non-social media websites you visit. Plenty to choose from: FreshRSS, TT-RSS, Sismics, etc.
Gitlab CE. If you're a developer or can otherwise make use of version control.
Gotify. Alerting on your containers. Has a good mobile app.
Heimdall. A dashboard for everything you're running.
Komga. If you're into manga. The best iOS app is meh, but the best Android app is awesome.
Mealie. Recipe database.
Paperless-ngx. Excellent for storing your PDFs and other digital life.
PhotoPrism. Basically Google Photos.
Portainer. Great for managing Docker containers/stacks.
qBitTorrent. Guess what that's for.
SWAG with Authelia. SWAG does reverse proxying with a Let's Encrypt certificate, and automatically renews it for you. Authelia provides MFA (Authy, Google Authenticator, etc) on top of it.
Vikunja. Todoist or Toodledoo without having to pay for features.
Wallabag. Basically Pocket.
Watchtower. Automatically updates containers for you. Can exclude the ones you don't want to update, etc.
Webtrees. Family tree research, if that's your thing.
YouTransfer. Useful for sharing files without having to use Dropbox, etc.
I have in the past run a Valheim server and a VRising server, too. FWIW.
I'll echo AGH being better. And there's a sync if you run two instances like I do. Wallabag is solid and its even better with Minflux as your RSS reader. Super tight integration to save from RSS to Wallabag. Love it.