The bridesmaid dress I like is sleeveless and my wedding dress is not. All four of my bridesmaids said they would feel comfortable in a sleeveless dress, and the two maids who tried it on really liked it, but I'm concerned that I'm violating some rule of etiquette. How closely do the bridesmaid dresses have to match the bridal gown?
Not so much that this should be an issue. Generally, bridesmaids should wear a dress that matches the formality of the bride's dress -- and that usually means in length. So if your dress is floor-length and this one is, too, you're pretty much fine. You just don't want to put your maids in casual sundresses when you're wearing a big, formal gown, for example. But as far as the actual dress style and details (neckline, sleeves, etc.), they don't have to match exactly. If your maids like this dress, go for it!
Bridal Party Fashion
Basics for Bridesmaids