Template contains file "image-condif.properties" this file define the transformation of image.
If area are empty sometine we need to remove some wrapper tag. Exemple : you need a box arround you area, but if the are is empty the box must be removed.
some time the filter on a image proposed by the controler is'nt correct. But we can change it in the renderer.
In a template html or jsp file you can use the tag imagetransform for create a filtered url to a local image, like a banner.
When your create a template, you can test if a area is empty or not and change the html. A simple example is if the sidebar doesn't exist you could change the size of the content zone.
The colors on template can be dependents from a web site.