You could go for the obvious tried and tested present, which would be flowers, but this is not a very original idea and it does not show much effort in your choice of presents for her. You could go for a fragrance, but then again this might be an obvious choice.
Lingerie is not really a good idea as this present would be mainly for you and not her; after all she may be happy just wearing something plain, so long as it is comfortable to wear.
The best thing to do when thinking of a present to buy for your wife is to ask yourself a few questions such as what are her interests? What are her ambitions? What are her favorite things to do? What does she dream of doing? What’s most important to her? Her family?
Choose a present which is relevant to her interests, loves, hates etc. And always exceed her expectations on price and quality.
Say, for instance, the most important thing to her is her children, a great idea could be a professional photo shoot of her and the children together and maybe a large canvas print to remember the occasion by!
The secret behind a great birthday present is to make sure she knows that it had some thought put behind it, and is relevant to her in a meaningful way.