What should I do to establish rights on my work? Does it depend on the country where it was created?
Yes - it completely depends on which country you are in. If you want to make it really fun, post it on the internet and then try to chase after copyright infringement in multiple countries.
Copyright laws of the United States: http://www.copyright.gov/title17/
Copyright laws in Great Britian: http://www.copyrightservice.co.uk/copyright/p01_uk_copyright_law
Copyright laws of Burkino Faso: http://afro-ip.blogspot.com/2011/07/to-z-of-african-official-ip-websites-no_18.html
What you have to do to register your image (file a form, put a copyright notice on it, rent a billboard, etc.) as well as your rights and options will vary from country to country. Best bet is to google the copyright laws of your particular country.
Regardless of what country your in one of the first things you can do is establish evidence that shows when the work was created (or when you claim you created the work).
You can do this using the free online copyright protection service Myows.
This can't prove that you created the work but it can establish evidence that could be used if you ever needed to defend your copyright.