Here's a few ideas, but most will not last through the cutting phase
1. Lay a piece of open lace underneath acetate and then pipe white coating chocolate over the design. You'll need a tiny tip or just nip the end of a parchment filled bag. Put in frig to harden and then lay over the cake carefully. It might be easier to make 4 separate smaller pieces. If you need to visualize this method, check out Whimsical Bakehouse cookbook.
Actually, if you know how many pieces you'll get out of the cake, you can pipe the chocolate to the size of the piece: Triangles for a circle cake or squares (even simpler) for a square cake. That way you can cut between the chocolate and not cut through it.
2. Same exact idea, but use Royal icing. Again, laying on the hardened finished pieces at the end...or have a small display cake, but add the lace on each piece after the cake is cut using an unadorned cake for guests.
3. You can buy silicon molds of lace patterns to roll over fondant or modeling chocolate.
4. Old favorite: dollies and powdered sugar, perhaps with cocoa added. Maybe you can find an antique with an interesting pattern. Conversely, do a white chocolate ganache and a "black lace" topping.
5. If you're any good at tempering, you can just make lacey squiggles and let them set up.
6. Take a photocopy of a beautiful piece of lace laying over a darker color, then take that to a bakery and get an edible image scanned of it. Cost somewhere between $5-$10 a sheet. Here's the TRICK: Run the backing over the sharp edge of a counter to loosen. Put in freezer before removing backing. This worked perfectly on my test cake...failed miserably on my actual library cake, probably because I was too focused on other things.
Even easier: take your finished cake and let the bakery put the image on top.
Okay, I'm out of ideas. Off for more coffee.