Facebook, images and copyright?

[bcnu]

It's great that you're even AWARE of the copyright issues; so many people simply ignore them.

Basic rule: you cannot publish/distribute copyrighted stuff without permission. You can be sued.
Not everything is copyrighted (other than music recordings published by US authors in the USA, which are ALL copyrighted, either under state laws, prior to 1972, or federal).
You have a limited license to download and VIEW/save an image that the copyright owners uploaded.
SOME copyright owners authorize additional distribution freely, or with attribution (e.g., CC-BY) licenses.
Some websites require contributors to authorize OTHER members to modify or redistribute their works within the website (e.g., you can "share" things posted by others, but not outside that membership).
Most do not.
Works by the US Government are not copyrighted at all (in the USA).
Works published by US authors in the USA prior to 1923 are not copyrighted. Anything AFTER that, and anything not "published" prior to 1989, is subject to varying rules. See linked chart below.

Bottom line: You have to assume everything you see is copyrighted until you can prove it's not. If you make a mistake and the copyright owners object, you can be in trouble.