Build them in. Simple built-in bunk beds with uniform wood, with simple unadorned bedding, and thoughtful lighting is appropriate for adults or mature teenagers sharing a room. The grown up color scheme of grays and purple asks that occupants be respectful of the space and each other.
Create mini rooms. A more elaborate structure that creates four mini rooms with stairs, dedicated wall lights, shelving niches and elaborate detailing can only be done in a large enough room with tall ceilings. The large gray painted structure takes on architectural identity in its scale. The red mirror adds a little punch.
Individualize each space. A smaller space and free standing furniture still allows for individualization. Decals with quotes for each sleeping bed, wood paneled wall with a tree shaped coat hanger create a cabin-retreat vibe without being too overt.
More decals and bright decorations enliven the space and make this bedroom feel less like a dormitory.
Create activity zones. By stacking the beds, a separation of sleep and study can be created using each zone for a specific function and not giving up too much square footage for either.
One of my favorite uses for a bunk bed is the lofted-bed-plus-desk combination. This works really well in the dorm where you don't necessarily want to sleep under/over a new roommate. Each occupant gets his own sleeping and working space.
Connect two bunks. An L-shaped bunk-bed configuration is an interesting way to fit even more sleepers in a smaller room.
Theme it. Don't be afraid to have fun with the idea and pick a theme. Wouldn't this nautical theme be terrific in either a beach house or a children's room? The round windows function as portholes.
Add a little adventure. A green forest-inspired room would work well in a mountain cabin retreat or a child's room.
Make it fun. Indulgent parents might even allow slides in lieu of ladders to promote bunking.