i resize portrait to 256*256 and then i can do,but problem with portraits is that these are not good photos because most of them are smiling
Enlarging those little photos to 256 x 256 won't work; you will lose all the quality of the photo. Just do searches, most time you will find photos to work with.
Before you start making faces practice some, with the many the many tools that come with photoshop; trial and error first. Then give them a shot.
In the preview you left it seems, you have to learn to align the facial features, and then the face won't be so bad.