Aeris Calendar will look in the "Themes" subfolder of the installation folder (ie. C:\Program Files\Aeris Calendar\Themes\). Images that do not have a theme file (.wct) associated with them should be placed in the "Images" subfolder (ie. C:\Program Files\Aeris Calendar\Themes\Images). You can also create your own subfolders for easier organization. Theme or image filenames that begin with "event" will not be available for random themes. These filenames are reserved for use with events, and this prevents a Christmas-based theme from appearing in July.