I've been using Horizontal SNES covers, actually, though I've only printed about 3 so far. I prefer the more authentic look on them. The verticals are awesome, but don't have that same rush of total nostalgia when I see them. They're just different enough to register as "not the same".
However, after realizing the extremely convenient NES spine logo was added and never on the original boxes, I had an idea...
I've basically been putting Vertical Spines on Horizontal covers. The SNES retail spines are just inconsistent enough to be maddening...they almost match up, with the logo-on-black general scheme, but the position of the logos, the orientation of company logos, even the brightness of that Super Nintendo icon varies. I literally just copy the Vertical spine region (7"x1" area), paste it onto a horizontal, extend the 9-pixel white line for the top "Super Nintendo" logo up to the top of the spine, and fill the gradient around the company logo at the bottom to true black to match the rest of the cover.
It looks really good! You get the wonderfully professional and organized look of the vertical spine, with the original wide box art. I love it. I assume that it's too minor a difference to bother uploading though, so I was planning on just using it for my private collection.