I run a company that installs pattern imprinted concrete. With a budget of 17k, you wont get a professional imprinted concrete driveway of 600m2 so knock that in the head. As "Slim" suggests, go with decorative gravel/stone.
For an area as large as you have, top quality materials and the correct concrete mix plus labour will cost you a minimum of €40 per square metre and that does not include groundwork. If you are being quoted less than this, then ask the contractor for a list of materials they will use.
The list should have the following included at least,
UV Stable colour surface hardener, 6mm polypropylene fibremesh re-enforcement, a super plasticiser, release agent (to stop the imprinting mats sticking to the wet coloured concrete) and most importantly, a top quality sealer. This final stage is most important as it will enhance the colour and add to the durability and the finished driveway will need a minimum of 2 coats of sealer. I can give you more details if required and my advice is free with no strings attached.
As for patterns and textures, I know that you should check out a website called brickform.com and have a look at the other patterns available. I am not advertising my business on here or promoting it. I want to enlighten people as to whats available for them if they look in the right place. My own website is accessible if required. You get what you pay for and you should insist on a contract as we do.