Here are some vintage ball gowns Varela can get some ideas from:
These two in particular are my favorites
Vavavoom for the first one and timeless elegance for the second gown !
I love these two as well. I would have removed a couple details from the first gown, e.g. the small bow at the waist and the bling on the skirt. But I love the irregular pleats on the skirt and its volume.
The 2nd one is a 1950s gown. It's very simple but I love the bodice. I think it would be a great neckline for Letizia. And because it's simple, it can showcase the jewels...