Hi,
This is the beginning of «Introduction of main files to meshing objects».
The aim is to identify them easier. I hope it’ll help. I will update.
I apologize for my english. It's not my native language. Tell me if my words aren't not correct and I'll update it then.

Part One : Identify the IMG.DDS
1 – IMG.DDS : You need 4 files.
The one is calling «Dropshadow» and manages the shadow of the object (it’s a difference with sunshadow for objects being outside).
The 3 other files have the name of the object you’ve cloned. Here for example “tableDiningBistro….”
You have to export them into a folder (Check File)
You’ll open them via a graphic editor like Photoshp, Paint Shop, Gimp,… I use Photoshop
By opening, you’ll see many exported files. Choose the IMG.DDS.

Here is an example of 3 opened files of the tableDiningBistrot :

The first one : We call it the bump mask greyscale.
The 2nd : We call it the specular mask greyscale.
The 3rd : We call it the part mask. It manages the colourable parts of an object. This TableDiningBistro has 2 colourable parts, so red + green.
Red is the first colour.
Green is the 2nd.
Blue is the 3rd. (The fourth image is an example of a part mask with 3 recolourable parts (it means with red, green and blue parts : SculpureUmbrellabeach).

See you soon for next files or steps.

I have some pictures of the Dropshadow for you, Anouschka.
The first is from the Dropshadow_IMG you export with s3pe, the other how it looks with a mesh UVmapped on it, in the Texture Coordinate Editor in Milkshape.

Maybe you can add a little explanation, how you can view the _IMG files in s3pe, to choose which one you have to Export to be edited?