Hi,
the way to remove user pictures is using the exo powershell and the command Remove-UserPhoto "user1@Company portal .com" here is the reference to it https://learn.microsoft.com/en-us/powershell/module/exchange/remove-userphoto?view=exchange-ps just be aware, that after deleting stuff, it might be still visibile afterwards for ~ 24h until the cache in all cloudworkloads gets an update.
For the Bulk upload/update of the user pictures you could use powershell, but depending on the size of your organisation this is a bit annoying. I would suggest you using the tool from the ms partner code two. They have an free software called "CodeTwo User Photos for Office" and that one makes things pretty easy to mass update user profile pictures.