Not Exactly Sure Where to Start

[J.B.]

I bought an Alison Jr doll House on Facebook market.. The exterior has been fully painted and the interior has been primed. My intentions for this doll house was to kind of turn it into a haunted/horror house. With the rooms based off different ideas or maybe something from a movie etc. But I’m not 100% sure where to start since it’s already been painted and it’s supposed to be spooky should I just paint over the exterior? Should I remove paint first? Should I start with the interior and then work on the exterior? I’m just not really sure where to go from here. So I thought I would ask advice from those with experience. Thank you in advance! 

[KathieB]

I would not do anything until I've spent some time with the house. Eventually, it will speak to you.

Have you collected or made any of the items that will go inside? A piece you particularly like might be a way to establish a theme for a room.

Do you have a picture in your mind of how the outside will look? You might start by repainting the outside while you think about the interior. 

You should not have to remove the paint. If it is very dark or high gloss, you might lay on a thin coat of gesso as a primer for the new color.

[Khadi]

I would scour the Internet for ideas.  Try searching haunted dollhouses.  There is no right way to do it.  You should be able to just paint over old paint.  Another option is to wallpaper.  There are a variety of strategies to make wallpaper look old and stained.  If you are really struggling, perhaps you could paint it all white so that you have a blank slate like people often do when they sell a regular house.  Then the past owners vision won't interfere with yours.

[havanaholly]

1 minute ago, Khadi said:

...You should be able to just paint over old paint...

Unless you're trying to paint over oil-based paint with water-based paint.  I would sand the old paint to give it "tooth" and then prime it with a flat white (or off-white) interior latex paint or gesso for a primer.