You can use the cursor keys to cycle through the elements in a chart. The up and down keys move through the main elements whilst the left and right can be used to move through the items in a element.
On first inspection the shapes of the built in line markers appear to be very limited.
Both column and bar charts give you the option to invert the area colour of any bar that has a negative value. What is not clear though is how to control the colour used for the negative bars.