It's pretty cool how even at 3000 triangles, there is such a high level of detail on the skull. It really goes to show that you don't need things at extremely high resolution if it impacts performance. Especially if the image is a background image in a video game or something similar that users will probably not be paying much attention to anyway.
Adding on, it's really fascinating to see how fast you lose detail - even in the skull of 300, there is still a considerable amount of detail and you would be able to tell what it is without any further detail, but when we get to 30, it's completely unrecognizable. The cow is still somewhat recognizable at 64 triangles though.