Can I delete pictures off of my phone if they're already stored in my iCloud?

Yes, you can delete pictures from your phone if they are already stored in iCloud. However, ensure that you have iCloud Photos enabled, as this synchronizes your photos across devices. If you delete a photo from your phone, it will also be removed from iCloud and any other devices using the same iCloud account. To keep them only in iCloud, you may want to download them to a computer or another storage solution first.