dot/.local/share/gnome-shell/extensions/native-window-placement@gnome-shell-extensions.gcampax.github.com/stylesheet.css

.window-caption {
    -shell-caption-spacing: 13px;		/* current caption height is 26px => set it to half of it. TODO: better solution needed */
}

.window-picker {
    -horizontal-spacing: 32px;
    -vertical-spacing: 32px;
    padding: 64px 32px;
}