I did a lot of bedrooms, mostly when I'm bored or I need it. I try to concentrate on their favourites activities and show their personality into it. For example, I'm a drawing person AND a messy one, so it's most likely to have millions on pen and notebooks.
But because I'm hurt right now, there are millions of bandages and balms. So I'm thinking about what the character needs and what would it be like.
Echo's bedroom is basically showed here :
Really tiny bedroom, they unlocked another part of the castle for her, near her bed, so she can putmost of her and her father's things in it. You can't see it, but Echo loves blue, so there are mostly blue in the room. And yellow + pink, because she likes it too. Must go to the other side of the corridor to go to the bathroom.
Her dad's bedroom in the past (minus the cradle now, and some other things changed) :
Bigger than Echo's one (we only see one side on this panel), contains a bed for two persons, lot of furnishers and also plants and boards. Also there's the insignia of Taranis, because he's a proud man. bright colors. Also got personal bathroom.
Abel's bedroom (I don't even think I will need it but I drew it because I was bored) :

Clean with some decorations, lot of swords everywhere, hides a sword under his pillow. Bright carpet with the insignia of Taranis, but otherwise, he likes red, so some parts are red, like the drapes. Also got personal bathroom.
Hrodland's bedroom :
Small but comfy, lot of contracts and weapons everywhere, messy but comfortable. He likes to relax in there, so there might be some tea around. Hisbed is composed of a light covering and pillows. Lot of pillows. The interior has wood on the walls. Brown and blue. He got two insignias on the walls, one of Taranis, and one of Teutates. Also got personal bathroom.
there you go, for most of the characters.