Not sure if this will help but this was in the late 30's.
Have you tried to Google pictures of 1940's wedding cakes? Maybe search for some famous weddings during that time (i.e. movie stars that got married). There's sure to be pics of those I'd think. Or how about Time Magazine? Maybe they can help you out. They've been around forever and a day and I know they recently did a full spread on Grace Kelly (her wedding was georgeous) and Audrey Hepburn. I'd think they'd have something a long those lines.
I took a quick glance through the Google pics, and there were some that came up that might help. From what I can tell of them, it looks like they used a lot of string work in the designs. (Wish I had pics of my grandparent's wedding - they got married in 1941 but I kinda think photos of the wedding were a luxury during the war).
Anyway, HTH! Good luck.
Sounds to me that wedding cake was also something very few had, because of the war...hurry to get married and off they went.
I think you're right. And it seems that one ceremony for multiple couples was common, too, so I somehow doubt they had wedding cakes or at least what we would consider typical (shrug).
Or how about Time Magazine?
Oops, I meant Time Life Magazine! 
If you want to do a vintage 1940s recipe as well, there are numerous recipes for "war cakes" -- many are spice cakes with shortening and no eggs. They are quite tender and tasty (if I may say so). They are also vegan....
Just an idea.... 
I put a search in google: 1940's wedding cake designs. Here are a few sites I found with samples:
http://www.mcneillmanor.com/ShowGallery.cfm?ID=GLRY_01182004203832288267&qstring=gallery%3DLI%5F03182003133000000004%26start%3D43
http://www.fashion-era.com/Weddings/1945_old_wedding_photos.htm#Wartime_Weddings_
http://www.fancyflours.com/vintage-wedding-cake-topper342.html
http://blog.lulusvintage.com/2008/01/vintage-wedding.html
http://antiqueshoppefl.com/archives/rreed/Bride%20and%20Groom.htm
During the 1940's and World War II sugar, butter, and other ingredients were rationed. Therefore, cooks had to be quite creative in the types of cakes that they could bake. You might check a library or do an on-line search for cake recipes made with rationed ingredients so that your cake is authentic to the time period. Rationing would have also affected the type of icing that could be used on the cake.
I got this recipe from allrecipes.com:
Mom's Buttercream Frosting
A smooth creamy frosting, perfect for any occasion. This is an old recipe from the 1940's."
INGREDIENTS
* 1/4 cup all-purpose flour
* 1 cup milk
* 1/2 cup shortening
* 3/4 cup white sugar
* 1/2 cup butter, softened
* 2 teaspoons vanilla extract
DIRECTIONS
1. In a small saucepan mix the flour and the milk and cook over low heat until it forms a smooth paste with no lumps. Place in refrigerator and let cool completely.
2. With an electric mixer beat the shortening, butter or margarine and the sugar until light and fluffy. Beat in the cooled flour paste and mix until smooth. Stir in the vanilla. Use to frost any cooled cake. Makes enough to frost one 9x13 inch sheet cake or two 8 or 9 inch layer cakes.
Here is another site: Good Luck.
http://www.murraybrothers.co.uk/history.html
I know from my Grand-parents that weddings were small in those years and you were lucky to have some pictures of the couple let alone the cakes.
Good Luck.
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