Your first Image is how the vanilla xfce4 package is set up.
Your second Image is how the xubuntu-desktop package is set up.
Since you already have XFCE installed you need some more things to make it looks like that.
To make the first look like the latter you need to:
Download the Xubuntu theme
Open a Terminal and Type:
sudo apt-get install xubuntu-artwork hit Enter and type your password.
Download the Xubuntu Icons
While still in the Terminal, Type
sudo apt-get install xubuntu-icon-theme
And Download the Xubuntu wallpaper
Install them with
sudo apt-get install xubuntu-wallpapers
Then just adjust the panel's size and colors.
►Right Click on the Top panel ►Preferences ►Appearence and change the color.
While still in the preferences, go to the last tab to add the Applets you want.
If some of the Applets are not installed, install them with
sudo apt-get install xfce4-goodies
To change the Theme and the Icons go to the ►Menu ►Configuration ►Appearance.
To change the Wallpaper right click the desktop and then Desktop configuration.
Alternatively you can just install the
xubuntu-desktoppackage and it will set it up for you, though once you're about to login (if you didn't set it up to login automatically) you will have two choices:
Though i think is redundant to have two if only the aesthetics are the only difference between the sessions.