Thanks for everyone's comments and advice. There is nothing in the contract in regards to the creation or retention of anything related to illustration or design or a non compete agreement. I was never even classed as a designer and it was primarily a teaching position, with helping out with illustration on the side as they knew it was something I could do. However, a greater workload and responsibility was put on me later into the job in regards to design work that I felt wasn't something that was part of the contract. This was an issue that I hoped to address with the new contract in addition to negotiating the salary as it all seemed somewhat strange to be doing design and illustration work without that being included in the initial contract. I suppose as I enjoy designing and wished to build up my portfolio then I was happy in the initial stages to do that for the company. Also with it being a very small company I was hoping to help grow the media aspects of it (something I mentioned in my interview), but my boss has a million ideas that get built upon and then changed to something else (I'm sure others have dealt with clients who are just the same though)
To be honest I don't think my boss has much knowledge on issues such as this and perhaps expects the style that I have made for his company to be his property. I will discuss it further with him before I leave, as I wish to be as professional as I can, as well as watching my own back, but thinking about it I doubt it will cause a problem in the future. If they do wish to seek my services as a freelancer in the future I will be sure to make sure the contract is something that works for both parties.
It is an experience I can learn from though and I am excited to be giving freelance a go as it is something that I have always wanted to try whether I succeed or fail. Keep your eye on TIME magazine @Kevin-Longueil ;)
Again, thanks for everyone taking the time to help out!