In order to choose programs you have to think what applications you use now and see what functionality they offer. It is hard to say if your specific needs are met by just one package. Typically, as a graphic designer, you might be using the tools from Adobe. Those tools aren't currently available for Linux, but the company has announced plans to bring the tool to Linux. If you care you ought to send them an e-mail to show that this important to you.
Meanwhile you could look at "The Gimp," which is a widely used graphics application with a zillion plugins for all sorts of functions. The nice touch about this program is that it also works with Mac OS/X and Windows. So you can test-drive first to see if this application meets your needs. If this application is not sufficient, there are many applications to be found at Freshmeat. Let's hope you'll be among the fine ranks of Linux users.
Related Q&A from Brenno De Winter
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