It’s not perfect, but I did find a good-enough solution to this problem:
1) Install the Role Manager Plugin: https://www.shandyking.com/2007/08/01/wordpress-role-manager-plugin/
2) Change the Editor role to have all the same privileges as the Contributor role, PLUS “publish posts” (which is necessary for use with Flickr).
3) Set my contributors up as Editors. They have the ability to publish directly to the blog, which is more access than I want them to have… but at least they can’t do anything else.
Good enough for now.
Thanks!