Generate pentagonal spikes of arbitrary length, and snap them over a BlinkyTile! Currently only supports snapping over a single side. http://blinkinlabs.com/blinkytile/ For each spike you want, decide how long you want it to be, customize the design, and print it! I have printed these spikes on a Rep3 ("MakerBot Replicator 5th Generation Desktop 3D Printer") on the standard settings. (No support material, raft optional but recommended) I found the result fine. I expect it to work acceptably on any printer capable of thin-walled structures, and it should look great any any transparent or semi-tranperent plastic.