In my opinion, customers do care what the actual design looks like, especially when there are details in the design.
For wording/phrase type tees like the McCain t-shirt you linked to, the details are a bit less important.
But when you are selling t-shirts that are a bit more fashion orientated, showing the details in the design is important.
Having a photograph of the actual t-shirt in my opinion is a "best practice" for selling t-shirts. That doesn't mean you can't be successful without showing a showing an actual photograph (see: tshirthell), but from a customer point of view, seeing an actual photograph helps to show that the t-shirt is real, the business is real, and gives an overall more realistic view of the t-shirt the customer is interested in without leaving much to guesswork.
I think having multiple product shots is a good thing though. Showing the t-shirt closeup or showing the t-shirt on both a male and female model can help customers make a decision. Remember that you're not there to answer any questions the customer may have, so you want to make sure you can answer as many as possible with your website so they don't have to look around for an answer or worse, just leave because things aren't clear.
I like the threadless method because for those customers who want to see the design closeup by itself, the link is there
. You can also see the product photographed on models to see the fit.
I also like the DBH way of displaying the product
on the product detail page because the product shot is larger than most sites which helps to show the detail in the design.
Overall though, I like the bustedtees way
of presenting the t-shirts. On the main/catalog page, you get nicely sized images of *just* the t-shirt design that allows the customer to quickly scan to see if a t-shirt design catches their interest. Once you click on the design you like, the product detail page
is laid out very nicely. Clear photograph of the t-shirt above the fold, an image of just the t-shirt design, also above the fold (no clicking necessary to see it), add to cart button, size chart, inventory status all above the fold for easy clickin'