Windows renders the application image on top so it appears twice.
Update example file thumbnails on start page to have a consistent background (classic theme) and remove the old FreeCAD logos.
The EngineBlock.FCStd example file contained a corrupt Points file. A new file was created by opening the V0.17 version of the FCStd file, saving that file, and then copying that Points file into the V0.22 FCStd file.
It's a very OLD example BTW. See also #14583.
To check the problem recompute the original V0.22 FCStd file.
Result:
```
pyException: Traceback (most recent call last):
File "D:\BKG_Tmp\FreeCAD_0.22\Mod\Draft\draftobjects\bspline.py", line 113, in execute
spline.interpolate(obj.Points, PeriodicFlag = True, Parameters = self.knotSeq)
<class 'Part.OCCError'>: Standard_ConstructionError
20:56:32 BSpline001: Standard_ConstructionError
