Original post here. This image was researched by Bacchus at ErosBlog as part of the “Γ commission.” The research was originally published at Hedonix as “Γ 036 – Sexy R2 Unit.” Here is what Bacchus found.
A commenter on an Imgur appearance of a slightly photoshopped version of this photo (one that artificially accentuates the visible portion of butt-cheeks) identifies this as a photo of Meg Turney, who is a cosplayer and internet personality. Although that’s a somewhat sketchy attribution to be sure, it’s given some additional weight by this stock photo of her appearing in the same R2-D2 dress at something called the Streamy Awards. Too, these Pinterest posts ( 1 2 ) feature demure-ish selfies of her in a closet in the same dress.
For interest, there is an entire Pinterest board devoted to women wearing versions of the R2-D2 dress. While browsing it, I discovered a captioned version of the subject photograph that asks the question you were probably asking also:
The garment here pictured is not the same as that which appears in pintrist post 2, as can be seen by the seam on the right side. Also in that picture in the mirror you can see a red light on the back of the dress, not present on the featured photo. Based on this, I conclude the garments (and probably the people) are distinct.