Valentino did a great series of luggage for his winter show a year or so back (the "Valentino Airlines" show ((see the pic in my avatar))) and I think he's started producing them each season. They're ludicrously overpriced, but the monogram looks great.
But, overall, if you want designer with a logo and are willing to pay for it, I second SoCal's mention of Goyard. It's not exactly subtle, but still not as garish or showy as the LV monogram. And, it's actually very well made.
Hermes makes gorgeous luggage, too, but you could buy a decent used car for how much a suitcase will cost you. As for other designers, I'd avoid Prada for luggage, though. I have some of their duffles and I like them well enough, but I wouldn't want wheeled luggage. Same with Gucci, same with Christian Dior. When I graduated from college and got my first decent-paying job, I thought I'd be the coolest guy ever because I had designer luggage (one was Borbonese, the other was Dior). I kept smiling about it until I took my first big trip and it got the shit kicked out of it at the airport and ended up looking like I found them in a Salvation Army garbage bin. The Borbonese, in a beautiful shade of coffee brown initially, ended up with big whitish smears on it and nearly had the rolled-leather handles ripped off. As such, if you are on ANY kind of a budget or will traveling commercially (as opposed to privately or always with a valet), keep in mind that luggage that you will be checking will get similar treatment by airlines employees.
Therefore, I'd get a very GOOD, strong suitcase maker, not necessarily a designer who also happens to have a luggage license with somebody and who is more interested in a certain style/luxe aesthetic than in making a suitcase that will actually travel well. Some of these better brands would be Hartmann (mentioned above), Briggs&Riley, or Tumi. They are $500 suitcases that are really $500 suitcases; not $500 suitcases with $2200 of added branding. EDIT: RJman beat me to the mention of Hermes (I was typing just as you were posting!)
My dream would be to commission hard-sided carbon fibre luggage from Hermes -- extremely light and extremely durable. Of course, for as long as one flies commercial, there is no point in expensive (check-in) luggage (as opposed to purely functional luggage).