As soon as you create something, it's your property. You don't need to register it, others will need written permission in order to use your work.
If you're self employed you also own your work unless in your contract with a client it states they have ownership.
Public Domain
Until 70 years after death the work still belongs to you, otherwise the work is open to use by the public domain
Reproduction Rights
You own both he copyright and the rights to reproduce your work
Licensing
In some instances you may be asked to license your work i.e a stick illustration
You will gain a fee each time your image is used, you can limit the license to single use so you can get paid extra for use on printed material, exhibitions and so on.
Sound and music can also be protected: phonographic copyright looks like this:



