GraphicsThe genre you write in has some say in what graphics you pick. Hearts and flowers and fanciful flourishes abound for romance writers, while tombstones and dripping blood play well into horror. Since you're marketing *your* writing, think of the things that might end up on your book covers. Published authors might be able to get permissions from the copyright holders to use modifications of their book covers as site elements. If you are not the creator of your artwork, you are going to have to concern yourself with the copyrights covering the graphics you choose.
But, as part of your site design, what graphics are you probably going to be looking for? Please note: this is a separate issue from "content" pictures, which could include your book covers or any other pictures posted as part of the reading experience on your site.
HeaderThe header is the banner at the top of your web page that identifies your site. You may choose to have one header for the entire site or a different one for each section. If you do choose different headers, remember to keep them in "theme" - carry over consistent elements through out the graphics.
Navigation ButtonsThese "graphics" don't have to be graphics at all, but if you want something fancier than plain colors, you're probably looking at button pictures. The nice thing is they are easy to build. Try the Buttonator and see for yourself, or use a graphics editing program to build them--these will be covered in a separate post on "Basic Tools for Web Building".
Accent PiecesRather like the little touches around your home, accent pieces are all those "minor" flourishes that round out your site presentation. These are the horizontal rules, the bullet points for your lists, attention buttons, and the like. To get a better idea of all that can be considered an accent piece, head on over to the css Zen Garden and flip through the designs there.
Oh, and a nifty thing to note: all those gorgeous designs on the css Zen Garden are accomplished by changing the css file--the cascading style sheet. The actual html--where all the content is stored--is the same through out all the designs.
So, now you've got an idea of what you want your site to look like, it's time to decide *where* to put your site.