Customization includes there size, color, shape, whether they move or not, and their density. Also, objects on the one-line can be set so that they are only visible at certain zoom levels. This allows you to zoom into a portion of the one-line and show successively more detail as you zoom in. A find command is also available to allow you to easily locate a particular bus on the one-line. You mentioned contours earlier.
Simulator has the ability to contour the system parameters on the one-line diagram.
The output of the contouring is a plot very similar to the temperature contours seen in the newspaper, except a system parameter, not temperature, is being contoured. This feature can be extremely useful for rapidly assessing power system conditions in a large region. By using this contour any regions of low voltage are readily apparent. Also, a number of options are provided to easily customize the contour and the particular color mapping to use. See our Features page for an example contour of marginal bus prices.