its cool that you want to start your own contest.
But usually with art contests you should map and plan things out and have a direction / know what your doing with the contest before you introduce it. I am sure people will still work with you in pursuit of your euros though. Anyway, the reason being is if i enter a contest myself i want to know its organized. Organized contests usually tend to pay in the end instead of ripping people off. Now some organized contests sometimes are still scams but usually its a good hint that the individual wants to actually genuinly make a contest because they put the time and effort in doing so.
This is where figuring out what to do is important, now you might be able to still get a contest rolling anyway and i'm sure you will. But who you attract might be different, some people might not risk putting their artwork in your contest or trust the contest at all.
Telling us what you plan to do with our work is important. Entering a contest is more then just wanting money (sometimes its just money) we want to know what happens if we win. Will we get more exposure? Who has rights to the piece? Do you want rights? etc etc etc these are important questions.
For instance, if i entered a contest for 1000 dollars cash as first prize but the person who run the contest gets full rights to my artwork in return. That is tricky. He doesn't have to give me credit for it now, and he can sell it and make profit.
So in a perfect world, i would get 1000 dollars he would get lets just say it was epic, 10,000 dollars.