In this scene, Emilia Clarke's nudity symbolizes the character's nipples.
For example, in season one, Daenerys Targaryen starts out as a timid boner cushion sold to nomadic prince of violence Khal Drogo. However, by season three, Daenerys has transformed into an ass-beating warlord with a massive army and a retinue of freaking dragons, blazing her way through the desert and conquering every city-state she encounters along the way. As Daenerys grows into her role as the warmongering Mother of Dragons, her costume actually becomes more dragon-like:
Or maybe just more crusty. Astapor is a sweaty place.
Costume designer Michele Clapton created a series of seemingly-identical blue dresses for Daenerys to wear throughout seasons three and four, but if you look closely, you can see that the dresses gradually develop embroidered dragon scales. The differences become obvious when you compare the first and last episodes of the third season: