Problem with viewing files 100x100px.

[Lunna]

I have coppermine 1.4.10. I don't know why my gallery show thumbnails for every file, except files, which is 100x100px. It's rather nervous, cause we have icons in the gallery, which are exactly in this size. Some time ago thumbnails of this files also was showing - what happened? What can we do to make this file visible in album (in album we could see only [AD] instead of file thumbnail). Please, help us.
I have also one question - could we use a graphical icon with for example preview of file, in files with extension .rar or .zip, instead of their icon of 'zip file'. We wanna have every .zip file with another icon. Is it possible? Should we use some plug-in for it?
If you have any idea, help us

[Nibbler]

If you see [AD] then disable whatever software you are running that thinks the thumbnails are advertisements. Custom thumbnails are explained in the documentation.