don't need iCloud storage any longer
If you want to remove all photos, documents, data or disable iCloud library for your account.  Proceed like follow:

On iOS10:
Go to Settings > [your_name] > iCloud > Storage > Manage Storage from there you can disable, delete everything you want. 

For iCloud Photo library, you'll have 30 days to download everything stored there. 

Update:
To download your photos and videos on your iOS device, go to Settings > [your name] > iCloud > Photos and select Download and Keep Originals. On your Mac, open Photos, choose Photos > Preferences, then select Download Originals to this Mac. 
You can also select the photos and videos that you want to download from iCloud.com.

Further informations can be found here.