Ikea Bookcase Customization: Phase 1?

I've had two Ikea bookcases on either side of my TV for a couple of years now, and I've been thinking of interesting ways to spruce them up to fit the evolving aesthetic of my apartment. The biggest problem that I have with the bookcases is that they feel like two huge black holes, sucking tons of energy out of the space. I figured that a cool idea would be to add some type of door to each bookcase for some dimensional and tonal interest (and to hide a slew of tools and other unattractive items that I'd rather have hidden away). I'm loving the look of wooden slats these days, so I decided to strive for that aesthetic. I'm calling this "phase 1" of bookcase customization because I think that I'll add ...something... to the back panel of each at some point to lighten them up. Paint? Wallpaper? More wood?