Hi Themnax,
As for layout information files: See the Layout Viewer manual:
* Screenshot: JPG-file, size 480 x 360 pixel. The file name must exactly be the same like the layout file, including the extension “.roa”. For example: for the layout “Analogdemo1.roa” the screenshot must be named “Analogdemo1.roa.jpg”!
* Layout description: A short text about the layout in the normal, unformated text format, created for example with Notepad or Editor. Again the text file must have exactly the same name like the layout, in the above example “Analogdemo1.roa.txt”.
As for custom terrain: Just start the layouts from Layout Viewer. It recognises custom terrains with the same name like the layout and copies the custom terrain to terrain.jpg. For layouts without a custom terrain it uses the standard full ground.
Hope, that helps.
Willi