ideas for Eames Storage Unit configuration  

a simple addition...
...to the "4-bay" (in your picture) would be to add the smaller "2-bay" three drawer unit next to it.
Adding the smaller unit to the right of the larger one would create a longer
"6-bay" storage unit. (Much more elegant and streamlined total shape than the single 4-bay, in my opinion.)
I have had a 2x and a 4x ESU pair for about 15 years, and I always end up going back to the side by side configuration.
(I would blame Ray Eames, but that is Mark's thing...)

There aren't that many choices...
Current production from Herman Miller is either neutral or colored, in these configurations only:
1H x 1W, no doors
1H x 2W, no doors
2H x 2W, no doors
2H x 2W, with doors
4H x 4W, with doors
Modernica used to make (and maybe still makes) ESU knockoffs in custom configurations up to, I think, 5H x 2W. They let you choose colors, doors, panel materials, and drawers for each bay, so you could create nearly any configuration you wanted. Unfortunately, the ones I saw when I visited them were low quality; the very first message I posted here (linked below) was about that experience.
Here's an old photo of the 4x2 Herman Miller ESU in my wife's office:
http://www.designaddict.com/design_addict/forums/index.cfm/fuseaction/th...

2 x 3 sounds great
I also like the Herman Miller 4 x 2 pictured below, but it's not exactly like their new 4 x 2 (which doesn't have a perforated screen), and I wasn't able to get HM to find out the old colors on the back and on the left side. I have the new standard one like it and absolutely love the ESU.

Vitra
still builds their version with a perforated panel; it's pictured below. Maybe they'll sell you one if you ask nicely (or have a friend from outside the USA ask nicely).
Herman Miller was still using perforated panels in 2008; maybe they have an old one they can put into a new ESU for you.
If all else fails, I guess you could buy a new ESU from Herman Miller and then replace one of its X panels with a perforated panel from Modernica for around $55.

No 2 high x 1 wide?
Too bad they no longer offer a 2h x 1w... there goes my idea to pair it up with your 2h x 2w.
UNLESS... you want to go vintage. But in that case you will probably have to pay MORE for the little 1h x 2w than the larger 4h x 2w. The smaller one is far more rare (and expensive) than the one pictured at the top of this thread.
I'm sure Modernica would gladly bake one for you if you asked though.
Anyway, about the configuration choices: if you get ANY two (or any three) units, you will no doubt have tons of fun trying out all the different combos, planned or unplanned.
After all, they are modular for a reason, and will look great apart, together, back to back, in an "L' shape, or whatever.
(I do still long for the big 4h x 2w also)