I'm surprised nobody has commented on this yet.  I've been trying to decide if I should do this myself.  I honestly like the stuff grouped together - as long as it's not a full page of the same design.  I honestly feel that is over whelming.  I've seen other artists with sites like this were it's a full page of the same design.  It sort of turns me off, but it's 6 of one and half a dozen of the other really =).

Greetings!
 
Good question, and the answer is, in my opinion, that it really doesn't matter which way you arrange your gallery!  Make it the way YOU like it.  There are some very successful GCU artist who don't do much in the way of arranging, don't have featured products, etc, but sell a lot of cards!    
 
It has been stated over and over that many customers land here at GCU and never actually visit a shop, but, do buy cards.  My own sales support that.  Lots of sales come from BigDates and other sites as well.  What does it all mean?  You don't have to get people coming to your gallery to get sales.  (That's a good thing!)  And you don't have to spend hours moving cards around to get a certain look, unless you want to.
 
When people do arrive at your shop, they can easily search for the specific cards that they're looking for by using the search box.  
 
Personally, I don't arrange my gallery very often, and when I do, it's for my own amusement more than anything else.
 
Not sure if this is of any help, but, for what it's worth...
 
Penny