More ideas from Giulia
bunk bed tent... This gives me ideas.  Even doing it different and adding a sort of curtain around the top or up to the ceiling would be neat.  It is like a canapy bed meats bunk bed sort of thing.

Tent on top bunk . Source: Delightful Distractions - HOME SWEET HOME. Easy DIY using fabric or even sheets. For bottom, build in rod and use curtain hangers or tack Velcro to wood and panel for a more stationary curtain. For top bunk, hang from ceiling.