There are 17 iPhone backgrounds in that album; you'll recognize them as designs from this blog, just resized and reoriented to fit your screen. I may do another album with the Numbers Series, and then any future Twitter backgrounds that seem appropriate will be accompanied by an iPhone background. If there is any other design on this blog that you would like converted to an iPhone background that was not included here, simply request it in the comments or on Twitter, and I'll make it.
Personally, I don't have an iPhone, but I figured, oh why the hell not? How do I test them, you ask? It's a ridiculously easy system I made for myself in Photoshop consisting of two layers of an actual size photo of an iPhone that I sandwich the background between. So at the very least, I can tell you that the Hurley/Mr. Clucks background is my fave, with Numbers a close second. Ah, me and my imaginary iPhone :)