You can have more than one promo assigned to a stream. When you have multiple promos, you can change the order that they appear.
From your Dashboard
In the left side menu under VMcast, click "Manage Promos." This opens the VMcast Promos manager page.
Click "Change order."
You’ll see a list of your promos. Click and drag the promos into the order you want.
Now, your promos will rotate through the order you've set.
Default Example
If you have multiple promos playing, by default, VMcast will show three loop items, then the first promo in the set order, three more loop items, then the next promo in the set order, three more loop items, then the next promo in the set order, and so on.