That's a really good question. I know that I had to return an assignment but that is because it was defective so I was sent sent another of the same toy. I'd think that for sizing issues, that would be fine too. I've never tried returning an assignment product just because I didn't like the way it looked though (more sheer than the stock photo). Personally, I wouldn't return a free assignment asking for something else. I'd only return the product if it was the wrong size or defective... If I paid for it though, that's another story. but that's just me
I actually think that would make a great review, letting us know that it's not like the stock photo, what you dislike about it, etc. Anyway, I hope everything works out for you!