The Gemara (41) says one may not be mikadeish a woman until you see her. Rambam paskens this Halacha in two places: Ishus 3:19 and Isurei Biah 21:3. Raavad there also says if you don't know what you're looking for, bring an am haaretz with, so he can tell you if she looks good. Shabbos 53b brings a story where a woman was so tzanua that she was missing an arm and her husband never realized it because she was so tzanua. R' Moshe Feinstein in Dibros Moshe there (43:10) discusses maybe it was kiddushei ta'us, and also why wasn't the man praised for being so tzanu'a that he never noticed. But it is strange that she should be praised when the Halacha mandates the husband to see her and see that there are no gross misfigurations.
Rashi, Breishis 12:11 mentions that Avraham didn't realize how beautiful Sarah was until they went down to Egypt. Rashi's source is Tanchuma Lech Lecha 5. The Gemara (Bava Basra 58a; Tosfos Megilla 15a s.v. Arba also discusses this) also says that Sarah was one of the four most beautiful women who ever lived. The question is, how could Avraham have married Sarah if he didn't see her, for if he would have see her he would have known how beautiful she was!
This is the question of Maharsha, Bava Basra 16a as pointed out by Gilyon Hashas here on Kiddushin 41. Maharsha answers that Avraham did see Sarah before they got married. However, he hadn't looked at closely since that time, until he saw her reflection in Egypt. He thought she wouldn't look so beautiful at that point, many years after their wedding. But when Rashi says he noticed how beautiful she was, it was a surprise to Avraham that she was still so beautiful so many years later.