I need input from anyone who may have done something like this before.
I received an order for a fondant wedding cake (4 separate cakes each on it's own pedestal) where each cake is encircled with a very specific celtic knot and love knot crest on the front side. The top of each cake is to have something different. The top of one will have a cladough while two others will have the animal from an animal from the family crests and the last one will have a celtic cross. The celtic cross design is to be taken from a wall sconce that was provided as a template. My initial decorating strategy was based on it being a fondant cake and after researching molds/templates/stencils etc I realized i was going to have to make my own which didn't concern me as I've had to do it so many times.

Now the order has been changed to a cream buttercream icing and the decorating elements are to be shamrock green with gold accents and I'm going around in cirlces (in my head) about how best to pull this off and have it look elegant.
Any ideas? I best I've had so far is to use my original stencils/templates and copy them onto frosting sheets, trim the designs out and apply. Then brush the appropriate areas with gold luster dust. I see a mock up in my future for this weekend. Luckily the wedding isn't until the end of July so I have sometime to make it perfect.

do the individual cakes have to be round, or would the bride be open to the cakes in hexagon or square shapes? the reason i ask is because if you have a flat surface to attach to, you could put a piece of wax paper over the celtic knot designs, crest, cross, etc and trace/fill the designs with royal icing. let them dry for at least 24 hours and then you can attach them to the fondant with a little more royal icing. this is what i did when i made my st. patrick's day cake with knot work.

Thanks I could check with her. To be honest she (and he) seem very flexible. I had read about flexible royal icing and thought I might try that so it could go around the cakes. That's one type of royal icing I've never used though so I'm not sure how it'll hold on buttercream in the summer. However, it would definitely give me the detail needed. Any ideas for a nice shamrock green. Green colours (except lime greenand turquoise types) have always been a challenge for me.