Carrie Fisher has repeatedly said that she didn't wear underwear with her Princess Leia costume during the first movie since it would show, and Lucas convinced her there wasn't any underwear in space. Her breasts were taped to keep her nipples from showing and you can certainly tell she's not wearing a bra during some of the more energetic sequences. She was coked to the gills most of the time so it's not out of the realm of probability that she wasn't wearing anything but a couple pieces of gaffer tape under that dress.

Also, the top in that photo is not Princess Leia's dress from A New Hope. It is Padme's top from Attack of the Clones. Leia's dress does not have the seams down over the breasts and up to the shoulders; Padme's top does. My guess is the photo is a fake.

Bra no, panties...yes. You can see the outline of her panties (in some copies of the film) when she leans over and hugs the wookie after the tie fighter battle/escape from the Death Star. As far as the costume, you could be right, but it does look similar to what Carrie wore at the very end of The Empire Strikes Back (a white, high-neck gown). Plus, I'm not sure that that cropped photo with the text, is supposed to be the "panty" photo, at all. Of course, if it does exist, it probably IS a fake, but on the off chance that it's not.....

CARRIE FISHER FAKE PICTURE
 

Obiously a fake done from this original picture, sorry for vanishing up crazy dreams and hopes !

Leglod

Yes, but that's still assuming that the photo in the ad, represents the actual photo that's referenced in the text. Of course, I don't believe it's real, either. On the other hand, there's no reason that Carrie Fisher COULDN'T have posed for a photo like that. I've heard there's a risque video of Carrie (and other cast members), made during the filming of The Empire Strikes Back (topless nudity, at least). I believe Michael Jackson is rumored to have owned it.

Another publicity still of Gwen Welles, from the film; Nashville.

Publicity stills of Jane Birkin (bra & panties/topless), from three unknown films.

Publicity still of Lynda Carter (upshorts/pussy slip?), from the TV show; Wonder Woman.

On set/publicity stills of the stunning Samantha Eggar (in period underwear), from the film; Dr. Doolittle. A very mild EUF scene (which seems to be a trend in family films), has a shipwrecked Samantha lamenting the loss of the trunk which contained all of her clothes. The clueless Dr. Doolittle (played by Rex Harrison), tells her that the outfit she's currently wearing is the most becoming thing he's seen her in on the entire voyage, to which Samantha replies; THIS IS MY UNDERWEAR!

Publicity still of Zoe Saldena (in her bra), from the film; Star Trek (reboot).

Solved one at least: "Jane Birkin and Iain Quarrier in Wonderwall, the first production of Alan Clore Films, which will be released later this ear. Wonderwall is the story of Oscar, a mother-dominated scientist, who lives a lonely and solitary life until one day he throws an alarm clock at the wall in protest at the noise which is coming from the flat next door. The wall cracks and light coming though the hole turns Oscar’s room into a wonderful camera obscura. Peering through the hole, Oscar is able to watch Penny, the model girl next door, as she embraces her lover."

("this year" being 1968)