This wedding cake had grey doily lace piped on it in buttercream. The cake itself was also covered with buttercream.
I got a lot of feedback on this when I posted it on facebook because of the piping. I thought this was kind of strange, but I guess that a lot of designs like this are done with molds and fondant now.
This was NOT difficult to pipe. It didn't make my hand die, it wasn't all over the surface of the cake...THAT would have been a lot of hand-hurting effort.
I did this pattern freehand since it was just a round shape, but you could take a real crocheted doily and press it gently into the icing to mark the design, then pipe over the pattern. Even if you don't mark every detail it will give you enough to go on that you can do the pattern accurately. You can do the same thing with a piece of lace that has stitching details on it. Flatter lace won't work, but as long as it has some thicker stitching on the edges that will mark your basic pattern.
Kara Buntin owns A Cake To Remember LLC, online cake supplies at www.acaketoremember.com and www.acaketoremember.etsy.com