Odds are high that you have seen Frank's work if you have gone into an Urban Outfitters, Nordstrom, Target or watched a movie or television show where a character was wearing a beer t-shirt, especially a Miller brand.
Frank Keppler is a graphic designer and co-owner of Brew City Brand Apparel, the company that produced the shirt you saw. Or better yet, that I see once a month or so in a store or on TV because I know what I'm looking for. Frank's designs are commercial but his style is unique and pretty easy to spot. He finds a way to even make vintage look fresh and contemporary.
I haven't spoken with Frank in years but I love his work.
In the mid and late 90's I worked for the Keppler's in Milwaukee managing their retail stores and seasonal set-ups like Summer Fest., a few years before they were selling large wholesale volume to anyone except Miller beer distributors. As there business has grown I often look at Frank's work as an inspiration. Why? I'll damned if it isn't one of the hardest design jobs ever to have beer and Milwaukee as your only motivation for twenty years.