Luckily it sounds like a few swaps and or small additions could definitely get you the room you desire, without having to spend the money on a big change!!
First of all, there are so many ways to DIY some wall art for above your bed!! I had David Bromstad to the studio to give a masterclass on painting your own wall art, which is great because you are in total control of the look! But if you’d like something a little less abstract, this DIY Large-Scale Instagram Wall Art is such a great technique, also! It really brings a sophisticated touch to the room, while still being personal because of your choice of picture!!
As far as bringing in other, more mature elements, think about candles, mirrors, and vases. These are items that aren’t typically seen in younger rooms, because they don’t really serve a purpose for people that age! All of these are super easy to find in many stores (try thrift stores, too!) and come in many colors so you can bring in any bright pops you’d like!
Hope this helps!