Do you feel there should be a continuity within your inn and the guest rooms? Should there (without being an actual theme) be some sort of style that is followed in decor?
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I think that your continuity should be with the sense of place that you're trying to convey. Whether it's a decorative style, your type of business (getaway, business,wine country, rustic cabin, etc.), or the hospitality style of the innkeepers. What will bring the guests to you over some other place? It might not be a draw if every other place in town is Victorian or it might. Seems like most innkeepers that I know are drawn to making their place what's also comfortable for them. 
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No theme here. Two of the rooms are named for the families that owned the house. One family was 
own-home" and that room has quilts and is my feather-free room. One is more elegant but not fancy - no one that ever owned this house was fancy, The third room just is - nice but middle of the road between elegant & down-home.,
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I think it depends. My Inn is Victorian with period antiques throughout. Friends of mine own an historic manor house once the estate of a prominent local family. They collect furniture and memorablia from the county and era that this well known family represented (this family was prominent both historically and politically), so that is their theme. I also know of an inn that is so period appropriate that the staff dresses in clothes of the era as they do in Williamsburg. There is another one near by that does Christmas every day!
I think that one of the appeals of B & Bs is that we are each unique and offer our guests completely different experiences. As long as you have a theme and you stick to it, you are good to go.
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Never approach a bull from the front, a horse from the rear or a fool from any direction.
For example, one of my friend's B & B is a country farmhouse. They have lots of antiques, primitives in every room...so yes..they follow a specific theme. I like it..it gives a warm and cozy feel to the entire property. On the other hand another friend is high Victorian...again the theme carries throughout the inn. If it didn't I think it would not give the feel they want to convey with their property.
Having said that, I think it is up to the innkeeper to do what feels right and comfortable for them and will serve their guests in the best way.
I think the individual rooms should be cohesive, but they don't necessarily have to follow an across the board theme. However, when we first got here another innkeeper was pretty adamant about telling us to pick a theme and stick with it.
Lots of random furniture may or may not work, it depends on how it's presented.
Now if someone states their theme, yes, they should follow it.
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