As someone who travels more than just about anyone here, let me say that you're getting bad advice.
- Black is not necessarily a bad color. You just need features that make it unmistakable.
- Wheels, wheels, wheels. Unless you're walking down a lot of unpaved roads, don't carry it.
- You want to be able to use it again after this trip, so get something utilitarian.
Here's a mid-range suitcase from Lands End that can be customized by monogram:
22" Lighthouse Wheeled Carry-on from Lands' End
It fits into most overhead spaces, and the wheels are fairly rugged (which is key if you're ever going to take it anywhere other than a freshly mopped floor).
The most important variable is how you pack. If you're very good at it, you'll need significantly less space than someone who's clueless, which can be the difference between a 20" bag in the overhead and a 30" bag that you have to check.
I'm getting ready to upgrade my luggage (worn zippers, clicking wheels - 4 years of intense travel takes a toll). Here's what I'm considering:
Travelpro
But, if you don't want a rollerboard, check out this guy's blog:
Around The World With One Bag (Part Two) | Veritrope
He's got some interesting stuff there.