Wallpaper or paint them then hang a collage of favorite pictures.
bead board or shiplap will look beautiful on the back of those cabinets
Sandi: you might try a large piece of statement art work. Look at Marshalls and Home Goods for deals -- or clearance!
Hi Sandi: I hung a tall ship on the back of my cabinet. I used real short tacks, and it's been up there for 50 years:) I painted the back of the cabinet to match the rest of the room.