Try 3M Command Hooks, no drilling, no nails and they're removable and reusable. http://www.command.com/wps/portal/3M/en_US/NACommand/Command/Promotions/Search/?WT.srch=1&WT.mc_id=SE_exact_command-hooks&WT.seg_4=8544474085&gclid=CKir58HWzLcCFcR_QgodWRIAPA

Its a really lovely room! what a great place for kids to share. I like kids sharing rooms. I think you need another colour to tie it together. I would suggest a blue tone.... teal, navy blue, duck egg blue. to tie it together. Its a little to pale and looks sparse, but actually isn't. I would leave everything exactly as is, BUT, paint the back wall behind the bed teal and find a simple navy blue wall decal that is fun and kid- like maybe one with a sillouette of a boy and girl playing. I would paint the wall behind the sofa duck egg blue. Then I think it would suit both kids more and look more kid friendly. the blues will balance the pink and cream, but because you have a pale carpet i don't think it will look too dark. don't worry about making it totally kid like, its a room they will grow with, not a kindergarten, and it also needs to peaceful and restful for sleeping. besides with their art on the walls and bright toys everywhere it soon looks bright and kid like. Good luck!

What soft furnishings do you have. You could pic out one or two colours as an accent colour and use that as your Base for the curtains. I currently have cream hessian walls and have a duck egg blue and chocolate curtains. I'm currently making matching Oxford cushion covers for the settees . If you can't find what your looking for ready made buy the fabric and have bespoke curtains made for you.

you are thinking about the space right now. it looks odd, no doubt. 1) when you fill in with the furniture, just make sure the three steps are hidden. 2) consider three potted plants of different height, so the rectangle is complete. 3) glass bowl with Siamese fighting fish for each step 4) figurines of different heights 5) 2inch square wooden bar on each step up to the top of the rectangle. and complete the entire rectangle if you want with a smaller rectangle open in the center my suggestion is, there is a reason why this space ended up like this. it will look great once you put something there. things like these are what make your house unique.