Looking for Shelf Ideas

[Keebler Elf]

I want to put some backing on some cheap wooden shelving units that currently have no backing so that the wall doesn't show through the shelves. What's a cheap material I can use? I can tack them to the back of the shelves. Looks don't matter as I'll paint them black to match the shelves. I was thinking something like that old, thin wood paneling that people used to put in their basements but I haven't seen it around in years and probably isn't cheap anymore. I thought about cloth but I'd rather something solid.

Any ideas for some cheap backing material?

 

[salsaverga]

wouldnt mdf board/sheets be a good fit? relatively cheap and thin enough no?

 

[Robert Mugabe]

Keebler Shelf?

 

[Keebler Elf]

Found some chip board at Home Depot and that should work perfectly!

 

[Ponderling]

1/8" Luan plywood panels would be my go to.
They hold paint better than chip board IMO.
Chip board has lots of glue that I have found can give uneven paint adhesion and reflection if using anything other than flat paint.