Paint them. Draw pictures on then & paint the design on. I painted a small one 3 yrs ago. I wanted purple & couldn't find one so i painted the color i wanted. Have fun.
I wallpapered mine.
Afton: here are some good ideas
If they are fabric shades you can dye them either solid or dip dye for an ombre affect.... https://www.ritdye.com/instructions/how-to-dye-a-lampshade/
They have 2 formulas, one for natural fabrics and one for synthetic fabrics.
I used an old lamp shade to line a metal basket to update the boob light in my hallway. https://www.girljustdiy.com/boob-light-makeover/