Is it illegal to use someone else pictures and pretend to be them on facebook or online in general ?

[bcnu]

The photographer owns the copyright. Others have only the limited right to download and save a copy for their own personal, private use. Posting them anywhere else requires your permission, as you own the exclusive right to duplicate and distribute your original works.

File a copyright complaint with every website where you find your copyrighted works being used without your permission. They MUST "promptly disable" those files unless they want you to sue THEM for what some ignorant member uploaded to their site.

You can register hundreds of your own copyrights for one $35 fee. This gives you the right to sue for up to $150,000 in "statutory damages" for each photo used without your permission, not to mention your attorneys' fees. 17 USC 504, 505.