Old damn mockup I had laying around:

First bucket would be recommended by the room in its values, indicated by the ☺ and may just be automatically applied to the image
This does cause some problems where there's one image uploader and many images.. and also some user error margin added cuz if you have the wrong panel highlighted, you might upload an image publicly if you're relying on the computer to do it for you.
All other buckets are saved in order of most to least used... 'n maybe you can configure to prefer private uploads / some default bucket over public uploads