While the use of graphics and backgrounds can have a positive effect on the readability of your Web pages, I find that their use, more often than not, have the opposite effect. In general, backgrounds should be subtle so as to enhance the readabilility of text. I find most backgrounds with textures counterproductive to the this goal.
Lighter backgrounds work best for the presentation of text.
Darker backgrounds often help set off graphics. For an excellent discussion on the use of background colors and the presentation of text, check out Net Tips for Writers and Designers . This site offers the best discussion of this subject matter I've come across. Graphics Techniques for Web Page Images . The following list of sites provide an excellent source for free clip art and graphics.