OK...this is hereby formally solved.
https://www.wincustomize.com/skins.asp?library=32&SkinID=1929
What went wrong?
First I thought it was a dodgey zip....and sure enough you 'could' have zipped with 'relative paths' intact so the file would unzip with folder name added.
But...
That wasn't it....3 test ups later it still wasn't working....renamed files, etc...no help.
Then clever me looked at the preview image....640x480 jpg.....900k?....what's that negative compression?
Sure enough, it was infact a renamed bmp [bitmap] posing as a jpg.
That ain't gonna work....not in this laddies' lifetime.
Graphic proggies can convert a bmp to a jpg, etc....but it definitely cannot be achieved by editing the name.
All you need do is 'save-as' and find 'Jpeg,jpg format' and you're laughing....
Put ya money on the fridge....