O.K. found myself the right link/click in the meantime....
Then it says:
Add thumb for a girl 'Eva Green'
To increase the quality of the preview thumbs, we're now accepting submitted face-shots of the models.
The image must be
- size of 120x120
- .jpg -format (quality of 100% if you can select it when saving)
- cropped face shot of the girl - to see examples, check Peachy18
All right, going to search for a good shot with full facial nudity...