Great job on the skull and congratz for creating a profile and sharing! My first suggestion is to worry about details later. The place where you can improve most is with proportions and that is best tackled while not confusing your brain will all kinds of details. Also, try an iterative approach to drawing, it's a really fast way to improve. Here is a video from Sycra explaining the method. https://youtu.be/k0ufz75UvHs But most of all, forget about details for now. Once you get drawing, proportion and perspective down then it doesn't matter what details you add because your foundation will be solid. Keep it up! and keep sharing!