This is a really good idea kaz (of eagle's) I think I may copy you both, as you say it gives you an idea of how you are improving, and I can certainly see an improvement even in this short space of time.
I know what you mean about the butterfly. It has a looseness that is attractive in itself and it is so easy to overwork things. Plus the question of "what do I do now to improve it?" when in your head it is "done". I guess you could always call it v2
A good chance to add extra sketches too, as you do challenges or if you get carried away sketching lol. Good luck