I love fully themed cosplay and LARP groups. There are a lot of folks who go all out to craft costumes of a favorite character. It takes a huge amount of effort to craft everything, from your clothes down to your shoes, weapons, and individual personal items.
Doing it was a group kicks it up a level. One person with a detailed orc costume is neat. A whole troupe of orcs with detailed costumes is amazing. When they go to the effort of putting together a campsite, complete with themed tents, banners, and equipment, the experience is amazingly immersive.
Beyond that there are...the Warhammer 40k people. They recreate entire battlefields. This gallery of shots from Elysian Trooper is just mind boggling. You'll not only find amazingly detailed costumes of Imperial troops, but field gear, full barricades...and two complete heavy weapons emplacements.