This is where most of the action happens so I've given it a separate page.
Agenda Widget can show in three different "Row Style's":
- Date Icon: Shows an icon with the date to the left and the event details (time, title) to the right
- Date Row: Shows the date in its own row, then every event for that row in a list until the next day
- Inline: Shows the date, time and title all in the same row
You can also modify display of buttons and toolbars. Both of the toolbars can be disabled and replaced with buttons if you like as shown in the following pictures (the buttons have a red arrow pointing to them):
Button options are accessible by going to: Setting->Customize buttons
Themes and skins are also changeable. Changing the theme loads some preset settings which can then be further customized. Changing the skin changes the actual images used for the background.

Themes and skins are accessible in Settings->Customize Style->Themes/Quick skin change
As mentioned, this is just the tip of the iceberg, most of tyhe colors of text, row header colors, skin elements are modifiable/disable-able etc, just have a play around!