Any line must be at least two pixels wide or else it will flicker. Complex charts should be broken down into segments and turned into multiple charts. You should not put so many numbers on a chart that the audience is unable to figure out the point of the chart. Don't rely on showing a complex, illegible chart and expect the audience to be able to follow your learned discussion. It insults the audience and shows that you didn't take enough time to consider them in your design of the graphic.
Charts are the worst graphic offenders.
Figure 2 shows an example of a good chart graphic. There must be sufficient contrast between the text and the background. In Your Electronic Presentation We ask that you don't use photos that take up too much memory for the computer's size. Also, you should refrain from showing photos on equipment that does not have good resolution, as they will look blurred. In Your Electronic Presentation Clip Art consists of already created graphics which have an astounding variety.