According to the API documentation there are only 5 different homescreen templates available. However the widgets comming preinstalled seem to use different templates which are not listed. For example, the calendar widget shows 3 rows of text, but every row also has an icon. Another example would be the contacts bar or the program icons bar. Those use a 4 buttons layout not listed either. My guess is that there are some undocumented layouts. Another possibility would be that those widgets were created using a wideimage layout. I doubt that however, since those widgets have "sensitive" buttons which would not be possible using a wideimage layout. Also those widgets are not WRT based since they feature transparency.
Does anyone have an idea how I could make use of these layouts myself?