My fiancé won’t let me rearrange the spare rooms in our house?

So this is exactly why people say never to move in with someone. Only buy a home together. My fiancé had JUST purchased a new home shortly before we met. He asked me to move in with him very early on of us dating. I was hesitant at first, but agreed to. It would have made no since to expect him to sale a brand new house.

We live in a four bedroom house. Before I moved in, he had each room decorated. One of the extra rooms is for his two children. The other is the children’s “game room.” The third is the guest room. I understand why he had things arranged that way prior to me moving in. However, of course since moving in I would like to rearrange a few things. I personally would rather not have a guest room in my house. I would prefer people to stay at a hotel or elsewhere when visiting. My fiancé is the complete opposite. I am willing to compromise and keep the guest room. However, it needs to be redecorated. I HATE the way it is currently set up. The bed set is dark and looks outdated. He also has photos of HIS family plastered across the entire room. I think it looks tacky. I want to change the comforter set and remove all the photos of his family. He can put them in a photo album. I also will have friends and family visiting now, and the guest room does not feel welcoming only having photos of his family. I understand keeping the game room, because my fiancé and I utilize that room a lot. Mostly my fiancé, because it is like an extra man cave for him. The game room couch turns into a let out bed. Which is where the kids slept the last time they visited. I think the extra kids room is a waste of space. The kids do not live with us. In fact, they live in an entirely different state. My fiancé is in the military full time, so they won’t live with us until he retires. By then we won’t even live in this same house anymore.

Updates
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The children and his will family probably visit us ONCE a year, if even that. My fiancé visits them at their hometown WAY more often. I want to turn one of the extra rooms into my yoga room. I suggested we keep the game room, and get rid of the bed in the children’s bed. Then turn that room into the guest room. He gets fussy whenever I bring it up, and is refusing to do so. How do I go about this?
My fiancé won’t let me rearrange the spare rooms in our house?
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