Thanks AruN and Hans for your tests [:)]

The old house model cannot be imported correctly, despite using the trick you described:
- use original 3ds file, convert images to jpg, delete original tif, then rename jpg to tif.
- I also tried to change the 3ds file: using a text editor I changed all references of tif to jpg, then I changed images to jpg. No success.

I wouldn't try to edit a 3DS file with a text editor, because it contains various data used to validate file content length. But no problem to view its content to find out the images files it references.
Did you move the images files out of the tex subfolder?

The tarantula can't be imported because the 3DS files doesn't contain any 3D faces (only two lights).

The excavator data is probably incorrect since Autodesk's FBX Converter reports the same issues (like the two models of Model3D.biz I spoke about in the first message of this thread).