Thanks for all your support!! It’s so sweet of you to help your nieces with their room!
This wall is interesting because of the placement of the window, which prevents a symmetrical treatment for both beds, like headboards. But that’s okay! There is still a lot you can do with it!
Have you thought about a mural? The DIY Watercolor Mural I did in Maya’s place seems like it could fill up that unconventional space, bringing color and creativity and giving your nieces a chance to get in on the fun, too!
Another option is to kind of fake some symmetry! Hang curtains over the window above the right bed, and then install a curtain rod over the left bed and hang matching curtains there, too! They would act similarly to headboards, and if you chose a fabric that isn’t too sheer, the window wouldn’t always be obvious!
I hope these suggestions help!