When I was visited by the kids SW's, they wanted to see the room. They did not expect it finished, they just wanted to see it, make sure it was safe and clean, get an image in their head of the child sleeping in there. So no, I don't think they'll expect you to have a totally finished room, or at least that isn't what most of them are looking for
I 'nested' for every one of them. It kept me busy and it was fun picking out things. I had a bed, wardrobe, shelves, drawers etc ready. With the girls, I left them to pick the colour of the walls, the bedsheets etc etc...then I had a sudden buying and painting spree right before introductions!! They loved picking out the colours for new rooms, that was something they couldn't do in their foster homes
With DS, I did up DD1's old room. Paint peeling, marks everywhere, and so on. I went for a green and blue theme, because they are my favourite colours...no other reason! I got some of those stickers mentionned which you can put on the walls, they look good
DS hasn't suffered in any way for having a room which is part blue. Or a decor theme chosen entirely by me, because I wanted it. If he ever wants it repainted I'll do that