Need advice on my sad beige home

Help me. I’m about to close on this home at the end of this month, and it needs some serious color. The second photo is what I planned on doing with those alcoves on either side of the fireplace, but I’m starting to wonder if those spaces look too big to waste on shelving alone? Should I only shelf half of the wall on either side? Or the whole thing?

The other thing I’m not sure about is the wallpaper. I’ve always preferred bold colors and patterns, particularly dark and jewel tones. However, I also like to switch up my color scheme every now and again, and I’m worried about picking two busy of a wallpaper. I don’t want it to look too busy, especially when the shelves are full, and I also don’t want to commit myself to one color scheme in case I get bored with it in 5 years. I need suggestions.

Would love to see wallpaper suggestions as well!