5520 on the Wonder did not have the steamer trunk.
We managed just fine without it, although we only had 3 people in our cabin. We did have a fair amount of luggage, since we spent 3 days after the cruise at Disney.
Some of the things that helped us - we moved the life preservers under the bed, which increased the closet space we had available to us.
We also brought our own hangars, which helped to keep the clothes organized too.
Also, our 9 yo DD, loved the upper berth. When she was in the room, that was were she hung out, along with her "stuff." She didn't have much of her stuff cluttering up the room.