Yes, your lace dress can be altered and will look and fit a lot better as a result. There wouldn't be too many brides who could walk into a store or order a dress online and find the fit is just perfect...so rest assured if you aren't entirely happy with situation.
Sometimes dresses don't arrive as is hoped and it's very necessary to alter them. When you look at the dress you'll notice it's made up of several layers to support the lace and form the dress that's why it's important to alter it correctly.
Inside a lace wedding dress.
The dress below is lace and the first photo shows a dress which is very straight and just doesn't flatter the brides figure. With some gentle shaping a different look was achieved more in keeping with the brides shape.