Ideas for designing an attic bedroom for 2 girls?

My parents had a new baby boy so now my sister has to move into my bedroom which is in the attic. My room was only designed for one person and there's no way another bed will fit in there the way it is at the moment. It needs to be completely re-designed. Do you have any ideas? Or do we need to like get somebody in to do it?If we do,do you know of anyone like that in ireland?Me and my sister both have horses so we would like our room to be 'horsey'.Any ideas?