Here's some photo threads that show the country:
Antwerp: http://www.skyscrapercity.com/showthread.php?t=756508
Brussels: http://www.skyscrapercity.com/showthread.php?t=583178
Flemish Coast: http://www.skyscrapercity.com/showthread.php?t=1200625
Flanders in general: http://www.skyscrapercity.com/showthread.php?t=1241945
Belgium as a whole (lots from Wallonia): http://www.skyscrapercity.com/showthread.php?t=807016
Generally speaking, Flanders is more urban while Wallonia has more nature. The food is good everywhere, so are the people (for the most part..). I don't recommend Brussels for your first visit, it's a very interesting city for an urban explorer but it may be a bit too chaotic and dirty for the average tourist. Bruges and Antwerp are better introductions to Belgium.
If you want pretty buildings in large cities go to Flanders, but if you want hills, industrial archaeology and forests you should go to Wallonia. Things to do are cities like Ghent, Bruges, Antwerp, Leuven, Namur and Liège. Nice nature are the Ardennes, the Kempen, the Flemish Ardennes, the Westhoek (if you're into WWI, for WWII you should go to Bastogne)
Also, if you're going there this might be helpful:
Not zones, but Regions, there is the Flemish Region, Brussels-Capital Region and Walloon Region.
Not Flandder, but Flanders, the word is a plural in every language: Vlaanderen, Flandres, Flanders. And not the French zone, but the Walloon Region, (though Walloon is an old Flemish word used to refer to languages derived from Latin).
French
Depends of what you want.
The French part is hilly, with lots of forest and lots of great walking.
The Flanders part is more flat, nearer to the coast it gets really flat, polders, which is great to see if you are not used to it.
The Walloon (French language) cities are mostly nice, the Flanders cities are more famous and I do like them a lot.
The one place that could not charm me was Brussels.
I highly recommend visiting Bruges if you haven't already, it's beautiful and full of character!
They are both well worth checking out.
