Yes, here are some ideas which might work
* Non-premium users should not be allowed to rename themselves inworld
* Make "Basic Resident" the default surname for new basic accounts
* Make Basics pay to TP
* Remove Basics' ability to fly and/or script
* Restrict all Basics' draw distance automatically
* Tax Basics 15% of all transactions (inworld tips, gifted money, etc)
* Add a floating tag to all Basics, saying "Saving to be a Premium!" or "One day, I'll make it!"
* Log out all Basics after 2 hours inworld
* Charge Basics 50L for a photo or 100L for an upload
* Remove Basics' ability to file ARs
* Restrict Basics to only 100 items in inventory
* Restrict Basics from posting in the forums