600 € !
anyway. my 0.2 €
Make the text more catchy. Maybe use a headline (as the first replier mentioned)
"Three Day Splash" or something.
Put essential info together.
Downsize the graphics.
There is not enough contrast between the tekst and the background. Try out some other colours.
And maybe use another program (indesign is made for this, or alternatively use illustrator - if you have access to the full CS2 suite).
Good luck.
And enjoy your 3 day splash
EDIT---
had another look
have some more constructive criticism
check your spelling
think about rewriting the entire text you used
maybe try another font
think about how big this poster is going to be printed
...
You'll get there, maybe start with paper and pencil to try out some designs. If this poster doesn't have to be made on computer, maybe try a collage or stick to the paper/pencil/marker thing.
Designing posters isn't the easiest thing to do, so be prepared to ditch some ideas, concepts or entire versions. You'll learn from every one of them.
Cheers