The store uses HTML template files, held in the "DesktopModules\Store\Templates" directory.
To modify your store's look & feel, you need to modify the appropriate template file. You'll need a bit of HTML knowledge, and also the following place holders (which should be wrapped in square brackets e.g. [IMAGE] and are replaced with product parameters at run time):
IMAGE, MANUFACTURER, MODELNUMBER, MODELNAME, TITLE, LINKDETAIL, LINKDETAILIMG, SUMMARY, WEIGHT, HEIGHT, LENGTH, WIDTH, SURFACE, VOLUME, DIMENSIONS, PRICE, VATPRICE, PURCHASE, PURCHASEIMG, ADDTOCART, ADDTOCARTIMG, DESCRIPTION, LOCALE, TEMPLATESBASEURL, IMAGESBASEURL, PRODUCTDETAILURL.
There's also a post here