OK, looked a bit into this. The prince does not have two wives. He divorced his first wife (a distant cousin of his) before marrying Ameera.
He has two children with his first wife - and apparently doesn´t want more children. Guess he is an atypical Saudi man.
Here is his first wife:

Edit to add her name: Princess Dalal al Saud
Actually I think this is the wife of Prince Abdulaziz Al-Saud. I don't think we'll ever see pictures of Al-Waleed's other wives.
I am not sure. Found this:
http://encyclopedia.jrank...Walid-Bin-Talal-1955.htmlquote from article: Name:
Al-Walid bin Talal bin Abd al-Aziz Al Sa’ud
Birth: 1955, Riyadh, Saudi Arabia
Family: Married and divorced Princess Dalal (married, 1976); children, Prince Khalid (21 April 1978), Princess Rim (20 June 1982); married and divorced Princess Iman Sudayri (married 1996); married Princess Khawlud (1999)
Only the first three wives are listed, not Ameerah. When did he marry her?? I was wrong about him only having had two wives obviously.
I am not 100% sure I am correct here, but it all seems to fit on him.