@dansup Something you need to sort now before users get used to it being free & noting other comments definitely not something to copy straight from Space Karen. Not a fan of bluechecks! Other options:

1) Notional fee for annual app big update or initial purchase for iOS/Android app
2) Donation message after every 25,50 or 100 photo uploads
3) Tier usage on .social, large collection users to pay for using service

Also your future plans, is this a hobby or do you want it to be main job/income?