I think you’ll really enjoy the Ninja 250. It should be perfect for bolting around Chicago. Many sportsbikes, including the Ninja 250, have a passenger seat/pillion that you can places bags or slings bags over. Check out the information page on bags at ninja250.org: http://faq.ninja250.org/wiki/Saddle_bags
Now, if we’re talking really serious photography, and you’ve got lots of expensive lenses and a few camera bodies you want to carry around, I’d recommend going with one of the camera-specific backpacks available at most camera shops. I’ve got a Tamron backpack setup like this:
There’s enough room on the passenger seat of my Versys to lash it down to the top of the passenger seat using an inexpensive motorcycle bungee web, like this:
The Ninja 250 has a few less points to lash down a big backpack than the Versys, but I suspect it’s do-able, and there’s always the option of just wearing the backpack while you ride.
If you’re worried about visibility–and you should be–you should also consider the color of helmet you buy. White or other solid, bright-colored helmets might go a longer way for helping you be seen than the color of your bike: http://www.bmj.com/cgi/content/abstract/328/7444/857
As for GPSes, it’s not cheap, but I love my Garmin Zumo 550, which was designed for motorcycle use (includes wiring and mounting; waterproof; works with gloves; option to integrate with bluetooth helmet speakers).