You have to do file, save as, and then it will show you a list of face file positions where you can store the particular face. This will save the file as a face set file with your custom face in one of the positions recognized by VX Ace. I haven't figured out how to save multiple faces to the same file yet though.

I mean the Faces in GCH Facegenerator are not compatible to RMVXA
Facegenerator
http://de.tinypic.com/r/29x7j0y/8
and here is the automatic generated face
http://de.tinypic.com/r/2qbvcsi/8

You can edit the generator to make it change the size to the default 96x96, but it looks like it doesn't resize the image or center it, so you have a lot of whitespace in the top left corner and the face is cut off on the bottom and right.

exact what i mean^^

When you select Save As to save the face file, in the drop down menu where you select GCH file or PNG image, select the option for Row 1, Column 1 and it will save the face as an appropriately sized and placed image for when it's imported into RPG Maker VXAce.

To save multiple faces onto one 'sheet' then you need to make sure they have the same name, for instance 'Eric' and when you select 'Row X, Column Y' just save each individual face in the next placement on the list. You will get the 'Overwrite' message, which is what stops most people, but it will work. Just don't forget what position you are on when saving multiple different faces (Normal, Happy, Shocked, Bemused, etc.)

Can you post a screenshot, please? Cause I don't see it.

If you're trying to make a face sheet (the 4x2, with eight faces) then When you do Save As, and select PNG:
Select PNG[www.dropbox.com]
You will be given the option to select how to export the image. For the first one, select Row 1, Column 1:
Export as[www.dropbox.com]
Then when you make or have the second face ready, do the same thing, but select Row 1, Column 2, etc.