Some working code ...
Qt Code: 
  1. void Dialog::beforeInsertFoto(QSqlRecord &record)
  2. {
  3.     //prepare data dor id - generated key
  4.     record.setValue("id", generateId("foto"));
  5.  
  6.     //prepare data for name - get it form the label in the ui
  7.     record.setValue("name", ui->fileNameLabel->text());
  8.  
  9.     //prepare data for image - get it from the label in the ui
  10.     QImage currentImage = ui->foto->pixmap()->toImage();
  11.     QByteArray bytes;
  12.     QBuffer buffer(&bytes);
  13.     buffer.open(QIODevice::WriteOnly);
  14.     currentImage.save(&buffer, "PNG");
  15.     record.setValue("image", bytes);
  16. }
  17.  
  18. void Dialog::insertNewRecord()
  19. {
  20.     int row = modeloFoto->rowCount();
  21.     modeloFoto->insertRow(row);
  22.     modeloFoto->submitAll();
  23.  
  24. }
  25.  
  26. void Dialog::getCurrentRecord()
  27. {
  28.     //get image filename
  29.     QModelIndex index = vistaFoto->currentIndex();
  30.     ui->fileNameLabel->setText(modeloFoto->data(modeloFoto->index(index.row(), foto_name),0).toString());
  31.  
  32.     //get image
  33.     QVariant currentImage = modeloFoto->data(modeloFoto->index(index.row(), foto_image),0);
  34.     QByteArray bytes = currentImage.toByteArray();
  35.     QImage image;
  36.     image.loadFromData(bytes);
  37.     ui->foto->setPixmap(QPixmap::fromImage(image));
  38. }
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I was stuck in this final lines and the loadFromData helped.
Now i can exchange png and other data between objects in the ui/my model and view / MySql database.
Just posting in case somebody needs this and for comments on optimizing this code.

Thanks