I recommend a blue sky brainstorming session
Organize your thoughts into three types
What Characters do we want to see (ex...could be costumes , personality, or lines they say)
What rooms do we want to do ( ex...we need a mourge room, a chainsaw shack ya da ya da.)
what themes do would we like to explore (ex...clowns, asylum, egyptian)
Then see what theme will serve as the best frame work for the most amount of the rooms and characters. As you have an old hospital you will most likely want to stay in that vein, that does not mean you cant stretch the limits and really explore them. Coulrophobia is the fear of clowns, why not have a ward of the asylum dedicated to treating that making patients confront their fears.
Now that I have said that I will answer your questions.
1. is changing the name every year bad?
Yes, it is. you may have a part of the name that changes but leave part of it the same. My haunt changes the theme every year totally different. It is always The trail of terror, then there is a sub name that describes that years show. It ends up looking like
Trail of Terror
maze of the minotaur
the trail of terror part stays the same but the sub name tell them what Im doing this year. This allows me to market the trail of terror and change my imagery based on the theme, I do tend to favor the art to have a monsters silhouette so that they all tie in.
2. is changing the name/theme a mistake since I actually have a lunatic asylum
I think that you can do alot of exploring of themes while still in the asylum framework. If you are a duck then dont try to be a giraffe.
3. would changing the graphic format impact my business? I’m thinking of placing actual pictures of some of my actors (in costume) on all of our media.
Keep your font and logo colors the same, change your images as you wish. I think using your actors is a great motivator.
4. Should we move the haunted house back to the main building? Do you think it would increase business even more being if it was in a 150 year old actual asylum.
No, lots of haunts do excellent business in a warehouse. Largely they do not care, they are afraid of mud if it has been raining and, afraid of the rain if it is falling. If the show is good then it does not matter where it is held. The theme becomes more sellable if it is in the right location.