Try propping framed photos, paintings, and collages on shelves.
Treat your items like art and your built-ins like a gallery space. Here books and found objects stand proudly one cubby over from paintings and sculptures.
Break up built-ins that are mostly books with an object here or there. For example, he bowl on the top right shelf here lightens things up a bit.
Cover up unsightly electronics with cupboard doors.
Place heavier objects on the lower shelves, and get lighter and more sparse as you go up.
If you have objects you know you want to display, work with a carpenter to create custom built -ns for them.
Find a balance between different objects. This is a casual arrangement that has a good balance.
So is this one.
You may want to protect valuable items behind glass to avoid breakage.
Consider painting the back of the shelves a different color or using wallpaper.