Cases are all a matter of personal taste.

As I like to have a few other rackmount bits of kit besides the A-100 itself (mostly an MCV-24 and a power distribution unit so I can turn the whole rack on in under a second with a single switch, which is surprisingly helpful when you just want to spend five minutes here or there sampling single notes), I have my A-100 housed in a G6 rackmount case. Here it is last year:

http://bytenoise.co.uk/misc/2012-12-16-5-test-card-f.jpg
http://bytenoise.co.uk/misc/studio-2012-11-15.jpg

I've since replaced the rack with an MDF one, but I don't seem to have any photos of that online yet...

Basically, if you have other rackmount gear too, I think it's nice to have them all housed together. If not, you can get some very nice eurorack cases that aren't racks. But it's entirely up to you either way.

And if you'd like to see some example eurorack setups, there's always threads like these on online forums: http://www.muffwiggler.com/forum/viewtopic.php t=1135&start=6460&sid=ae7fa4c4a0855f607b172c46ffffdcb2

All the best,
Zoë.