I haven't exactly done a spoiler COSTUME per say, but at one point I made a 3D sculpt of titan Eren from Attack on Titan, and some people on the 3D forums I was posting on got upset because there might be people out there who still don't know that Eren can turn into a titan... Go figure. Seriously, there will always be overly sensitive people out there who will complain about anything and everything. Just go with whatever you want. At this point, most people who are interested in Star Wars will know what happened in The Force Awakens, so the risk of upsetting anyone is minimal.