Winter weddings are easier to plan because the cost of most things is always less in winter than it is in summer. It's possible that what may be a small budget for a summer wedding can actually be a good workable one for winter. The reception venue which by far costs the most money followed by the decorations which usually consist of flowers is available for a lot less in winter.
To make your winter wedding absolutely fabulous, you need to spend intelligently and find things that will impress the guests and make the venue look gorgeous. In summer you'd usually line the entrance with bushes or rented trees, in winter you can use simple ice sculptures (one of each on either sides of the door) or large stone flower pots (the ones shaped like swans) and add white Christmas lights.
If you'd like more green, rent some Christmas trees and decorate them. You can even have one inside so guests will know where to leave their gift. Don't use too many Christmas themed items unless the theme itself is actually Christmas. If the theme isn't Christmas, too many ornaments, lights and trees will make your reception look like a department store.
Add touches of something warm and festive like fresh fruit bouquets for centerpieces for wedding tables and use deep shades of fabrics with a satin or pearl like finish. If you aren't going to feature a lot of any color other than white, try and avoid using silver or anything else that brings the white out even more. For scant splashes of color, use gold as an accent.