You should have a small closet/wardrobe & dresser in each room - and a chair. Regarding decorating - curtains/drapes that keep out the light at night and decorate to your preferences. This will be yours and should reflect what you think it should be. Think about what YOU would want/need on an overnight and that is what you do for amenities. The BedPosts innkeepers will be able to tell you the REQUIREMENTS - and there are a lot of them. In the USA (in my state anyway) after registering with the State for taxes and getting the business license from my City - hang out a sign - not so in the UK.
Also do not have anything that you would cry over if it was lost, broken, disappeared anywhere a guest will have access. Have locks on your personal space and where you keep supplies.
I do not have "themed" rooms. I named them for the families that owned the house - it was a residence until I made it a B & B. I bought quality linens - (no sheets over 350 thread count (wrinkles more likely with higher count, more expensive and they WILL get stained!), nice towels. Get a lot of CHEAP WHITE wash cloths and put a sign on that in the bathroom Makeup removal - cheap enough to toss, otherwise they WILL use your good towels and cloths which are more expensive. This will save tome trying to get the makeup out of the good linens. Furniture is sturdy and looks nice - some from antique shops, some from junk shops (you can always refinish or paint to make look like new. Get the BEST mattresses you can afford - add good toppers, bedbug encasements on mattresses, box springs, and pillows then mattress pads and pillow protectors (these are not pillowcases - they go on also) - the pads & pillow protectors are Health Dept required here. A bad mattress will bring complaints.
Ask as questions come
Once again thank you for such detailed advice.
We have the option of buying the internal furniture. In fact for a few thousand pounds we can have it all. We feel it is too cluttered though, for example there is a large double wardrobe that takes up too much space in the room. I'll have a look to see if I can find some wardrobe/drawer combinations of a reasonable size.
Fortunately there are new blinds installed in all rooms so we will probably buy some nice small curtains and have them tided back with the option to use them. We will try to avoid white as much as possible to avoid marks and stains. The slats should be total blackout and help with noise (we are on a main road).
I think personally I'd want a coffee/tea station. Somewhere to hang a few coats and shirts. Drawers for other clothes. Maybe a small desk and chair, if not then a small round table by the window. The rooms are doubles but furniture eats into a lot of that so we need to be efficient with space.
I think for small trinkets we will go to a few charity shops or boot sales and get some cheap things that don't look too ikea-esque. I have some nice sculptures and art but based on your point I wouldn't want to risk it.
There is an owners area downstairs separated from the rest of the property. This has a large bedroom, a lounge, kitchen and separate bathroom. This is locked so should have excellent privacy when needed. It currently uses a key but I might get a number pad system for safety.
Interesting about the sheets. I'll see if we can buy bulk for a discount. I assume I'd want minimum of 3 sheets for each bed for rotation and to cover quick changeovers. Do you use a dryer or just hang dry the washing? If people stay an average of 2 nights and we have 3 rooms that is a lot of constant washing.
I love the makeup removal idea. I'll get a little basket with them in and place them near the bathroom mirrors. That is the type of tip you only learn once you replace a dozen white towels haha!
Do you use zip beds? The current owners have beds that can either be a double (with mattress topper) or they can unzip and split them as two singles. Even if not a health requirement I'd want very good mattresses with protectors and mattress toppers for comfort above all else