What to do with a 8ft blank wall in my bedroom?

Some ideas that come to mind are - sponge painting it, use a stencil and paint on a design you love, make a faux shiplap wall, create something bold with stripes or a design (painters tape can help you with this).

Have you considered making easy to do wall art? You can get large sized canvas ready to hang and color them, spritz them with alcohol and hang them. This is so easy kids could be involved to cover the wall. OR hang your family photos there. OR do a family tree with tree branches and family members photos. OR make it soft with hanging a curtain rod and some sheers or curtains just to soften the room. There are many ways to make it as you want with a useful or atmosphere changing decor. Hope this will help you think of your own version of what you want.

Here are several ideas you could consider https://www.pinterest.com/pin/738168195149054677/