I drew mines on A4 but the actual size of the image is a lot smaller, maybe just bigger than A5. I found it a really hard drawing to do, I loved the photo so much and I don't feel like I've justified it as much as I wanted to. Like you I drew it rather quickly and it's one of those drawings that sometimes I love it but sometimes I hate it. I'd love to do it bigger so I can really concentrate on getting the skin exact as most of it just estimated.
I had a look at your one and gave you some comments, I hope they help