Great map! I found the Easter Egg pretty easily but here is a guide for those that are lazy ;)

Skull: 5 power switches around the map (there's one next to the staircase at Juggernog for reference)

Summoning Key: Found in the laboratory on a shelf. Melee and it will bounce to another location. Just follow it and you should be fine.

Worm: Found sitting on a table, pretty hard to miss, just open up the map and you will find it easily.

Wonderwaffe (Extra): There are tables around the map that collect the souls of zombies you kill near them. There is one by mystery box.

I'll let you guys figure the rest of the locations and such out so that it doesn't ruin the fun because this is actually a pretty good map and looks very well made. Good luck!