Hideous upholstery on modern pieces  

Knoll
Does a lot of contract / commercial business so I wouldn't be surprised if that upholstery is original.

Hovmand-Olsen
...

Not quite upholstery, but...
Not quite upholstery, but equally WTF!
http://cgi.ebay.com/VTG-HERMAN-MILLER-EAMES-CHAIR-PAD-KNOLL-MID-CENTURY-...

I saw those...
They look like placemats. And not good ones.

Kristiansen
...

Oh god...
I love this chair design but NOT with a print. This should be in bold colors like red and blue...just like the classic designs. Some things shouldn't be toyed with.

I found a company that 'upcycles'
Some of their designs are pretty shocking. Lets just hope they don't get their hands on anything decent
http://www.greeninmind.co.uk/retro-coffee-table-with-lower-storage-rack-...

Risom
...

Ekstrom
...
http://i752.photobucket.com/albums/xx166/dominicchadwick/Ekstrom%20Armch...

RE daniel poole upcycle company
Did you see the Richard Hornby sideboard I dont even want to know what they did to it, I am crying as I write this.

Not upholstery, but could...
Not upholstery, but could pass as.

Argh!
Imagine the roller coaster of emotions you'd experience if you happened upon these pots at a yard sale:
"Those handles look interesting, it almost looks like... HEL-LO, it's Dansk!
"UGH! Pastel floral Dansk....
"Still... it's mint condition Dansk Kobenstyle, at $4 each... I wonder if this stuff can be easily reenameled?"
"Just put it down... leave it for a lucky blind yard-saler to use and enjoy."

another one
Fortunately there is an antidote for this one. (I pulled these both from 1st Dibs)

WOW!
No words.....
http://www.rearrangeddesign.com/2011/08/post-in-which-i-transform-my-cha...

Actually, I'm not sure I'd call that "hideous".
The fabric isn't unattractive, if you like that sort of thing... But more importantly, the chair and ottoman are no longer mismatched, vinyl, or pretending to be something they're not.
I think she really improved that set by reupholstering it.