All visual cues should help your reader interpret your data.
Extra visual decoration will hurt your audience's ability to interpret the message of the visualization. This extra decoration is called "chart junk."
Exploratory vs. Explanatory: Is there a specific message you want to convey?
Interactive, dynamic, or static: Would you like the audience to manipulate or play with the information?
Think about medium: How will the audience receive/interact with the information?
Audience: Who are they and what do you want them to take away from your visualization?
Overview vs. Details: Do you want a big picture of your data or do you want to drill down into important details?
From Edward Tufte's The Visual Display of Quantitative Information