Ashley - being very familiar with this bug, any image will do. Or not. An image will upload successfully one moment, then not the other. The likelihood of the image being an issue is, having observed this error for a long time, 0. I could upload some images to make you happy, but all of them would as likely upload succesfully on my system as they would crash C2, so I don't much see the point.
You also don't get access to any settings options. It hangs before getting to the dialog where you input the spritesheet cell dimensions. I have observed occasions where the hang has solved itself after a few minutes and I am shown the dialog where cell dimensions may be entered - although these have been rare. More often than not I give it two minutes, then force-close and re-open C2.