Well,I was thinking this for a long time. It is a general tendency even now to think of Linux as a sub standard operating system. It is very hard to get going and is not very flexible.
While I was into Linux for more than 5 years, I found the time has really come now. Almost everything has come to a point where a designer can start with Linux. Below are the list of the softwares,which I think can kick-start your design career without investing a lot of money on costly softwares.
These are some of the potentials of the Linux to deliver to a designer. the only thing is, once you take a little brave step to love the command line, though not necessary, it will come in handy and help you a lot. And I am sure once you start with commands to do your job done, you will also appreciate it.
The best of all is, all these softwares are legally free, so there will be no license fee or agreement to anyone.
Happy designing :)