"concrete retail environments can act as an outlet for a larger online venue"

Could you unpack that? I really don't understand what you mean.

I'm guessing you're talking about brick and mortar retail stores acting as an extension of their online presence.  These are usually less about being a super effective retail environment, and more about being a physical manifestation of their company identity.  I guess it could be about high style, or high comfort.  Evo.com has their store in Seattle, which I feel is a great example of acting as a brand ambassador to their online customers.  Of course they have a bunch of cool things to buy there, but their staff is just as much a part of the experience as the building.  They've made a place where it's easy to talk about your interests, what products you like, etc.  There's a restaurant that shares the building as well which makes the store smell very tasty...  Anyway, I would just look at retailers who have a strong online presence/brand identity, and how they translate that to any brick and mortar stores they may have.

I could be incorrect, but it sounds to me like the OP is asking for examples of physical shops that provide an image for businesses that receive most of their trade through other avenues, in this case online.

OP, if that's what you're asking, I can think of a few examples off the top of my head. Taschen is a good example, where its few retail locations elevate its image. Rizzoli Publishers as well, with its recently closed New York store. The Vitra campus is worth considering in this context. You might also consider the recent acquisition of DWR by Herman Miller, which might have been motivated by the desire to have a physical retail presence. Other major brands that use this tactic include Normann Copenhagen, Svenskt Tenn, Marimekko, and Ralph Lauren. A different, but an analogous example, would be how major fashion designers put out a runway collection to draw attention, but also offer a toned-down, less expensive diffusion line. The Rolex Learning Center and the new Apple facility are examples, although these aren't retail locations.

Edit: Whoops, I didn't mean to basically repost what Matthew posted.

how about the Best Products Showrooms?

for example - The ‘Forest Facade’ of the Best Store in Richmond

oh nevermind. rereading "as an outlet for a larger online venue" and Best Products Showrooms were mostly dead by time of contemporary networked/digital culture.. 

perhaps to obvious but what about Apple retail stores?