question about copyrights  

you've taken your first...
you've taken your first steps into hell.
Unless you have a lot of money behind you just let it go, You're more likely to attract interest and disseminate your name if you don't try and protect your work or hide your light under a bushell.
I'm sure Koen can give you a much more considered response but I think at the end of the day if someone wants to copy your work (especially digital images) nothing will stop them.
I'm not sure where you live but here in Australkia there are a few Arts Law organisations that provide free IP advice through volunteer lawyers, there are also a lot of standard agreements you can download from the web.

This is only the start of an answer...
...but I am running short of time.
Copyright is a simple claim. It is limited to original text, musical and other artistic works, sculpures, paintings, motion pictures, photography dictionaries, you name it...but not industrial design unless the piece is given the special status of work of art.
Nothing specific has to be done under the Bern convention, but you may apply for registration. The subsequently issued certificate can be used in court as well as any other proof (dated publication, witness account etc.) Most copyrights exist 50years after the creator's dead. If it is a joint effort the last living creator's dead is the start of the 50 years protection.
Most countries under the Universal Copyright Convention require that the work is marked with a small c in a circle, the name of the owner and the year of first publication.
In the case of the vase the copyrights are claimed on the illustrations because that is what can be protected under copyright laws. The vase itself can only be protected under Industrial design protection laws, but they require that the registration is done before the product is made public. The way the vase was developed did not allow for the necessary secrecy.

Thanks a lot for the info on copyrights
Thanks HP and Koen for the info.I live in the Netherlands.Here you have some options from what i have read on the internet.First one is through the taxes office,they register your illustration but they do not keep copies of it so this is not very secure,it costs only 5 europer illustration.The next option is through a lawyer but that is very expensive.Other option is to put the "c" of copyright on the illustration to scare people off.And the last one is to register it in a kind of website to keep is as evidence that you made the drawing and registered there in case of a lawsuit.(this last one is very cheap)What do you think is the best option?I really don't know what to do...

Hangt ervan af doll...
It depends very much on what you want to protect. The important thing is that it is made public in such a matter that it is dated. It was not unusual to publish a logo or brandname in a small local newspaper. Just by keeping the newspaper you have proof that you claimed copyright (do not forget the c in a circle and your name) In all cases the copyright is not policed by anybody but yourself!! So, you have to go after possible copiers yourself. Before the courts your "proof" will be compared with whatever proof the other party wants to present. In the Netherlands intellectual property legislation is generally good and the courts are fast compared to most standards, so it should not be too difficult to protect your rights.

Koen
Koen since you do such a eloquent job of explaining your self you might want to explain about trade dress used mostly in products like the Eames lounge chair and defended many times by Herman miller , my rheumatoid arthritis is causing me problems so it is hard for me to type long desertions so i will yield to my esteem colleague

Bedankt !Thanks !....
I"m a bit "onzeker" but,i think i'll go for the "c",date,and my name on it,if this takes off then i can think about getting an author's right for each individual illustration.Thanks a lot Koen for the fast response.