I think the site is nice - it's clean and directly to the point. No huge hero and no click-throughs to get to the meat of your project. Prices for your posters seem entirely reasonable.
Tangent: I don't understand the fascination with one's own commit heatmap (or any other commit heatmap for that matter). Maybe it seems a bit too self-congratulatory? Vain? I don't know quite what it is, but it rubs me the wrong way and I wouldn't be interested in putting something up like that in my home or office. Maybe because it implies quantity over quality? Whatever the reason, your poster project is nice regardless of whether or not I would buy one.
Tangent: I don't understand the fascination with one's own commit heatmap (or any other commit heatmap for that matter). Maybe it seems a bit too self-congratulatory? Vain? I don't know quite what it is, but it rubs me the wrong way and I wouldn't be interested in putting something up like that in my home or office. Maybe because it implies quantity over quality? Whatever the reason, your poster project is nice regardless of whether or not I would buy one.