I am currently partial to the Cubitek Magic Cube Design for buiding an ultimate rig.
 
For your purposes the basic concept for the motherboard part of the case could be tipped onto its front (a 90deg rotation, leaving the mobo I/O panel facing up) and then be rendered in sealed acrylic and filled with oil. You could buy SSD's, external HDD's, and an external optical drive and mount them wherever you wanted, perhaps on an acrylic plate or shelf with all the connector cables custom sleeved and gathered in a decorative fashion.
 
http://www.cubitek.com/products/chassis/magic-cube-8/features.html
 
SSD's are attractive looking, especially Corsair's Force GT, then go with a big external HDD like this onë:
 
http://www.newegg.com/Product/Product.aspx?Item=N82E16822154430
 
And this for your Blu-ray burner:
 
http://www.newegg.com/Product/Product.aspx?Item=N82E16827151251
 
I wouldn't even need the additional HDD & Optical drive cases that the Magic Cube comes with, I'd just use the mainboard/PSU case and mount the rest on the top & right side panels of it, with attractively sleeved cables leading inside.
 
Anyways, that's my current mental image of a custom design unlike any other. I'm sure I'll finesse the details in the future. That's what dreams are for!