The anniversary wedding cake consumption is a tradition, but you might just want to preserve it as a memorabilia.
To preserve a part of your wedding cake to last till your first anniversary, you can put the cake in an airtight container to avoid picking up odors from other frozen items. Wrap the container in plastic wrap and aluminum foil, in order to block moisture.
For long term storage purpose, fruit-filling cakes are better than fresh-fruit ones.