The links below represent the best web sites dedicated to graphics and digital imaging for the Web. As you consider using graphics for the WBI, remember that not everybody has a T-1 connection to the Internet. The rule of thumb I use is to verify that my Web pages, including graphics, take no longer than 10 seconds to come up on the screen with a 28.8 modem. You should use the same rule for sound and other types of digital images. You can fudge on this rule as long as you let your audience know before hand what is happening.
Less graphics is more effective.
If you plan on enabling your audience to print out your page, you will want to avoid dark backgrounds with light colored text. If the graphic serves a purpose in the instruction use it - other wise stay away from too much graphics just to make your page look better. The same goes for video. By the way, you can always use the free graphics that are available on the web. Please observe copyright law.