Here is an idea of how detailed an ACEO can get. Remember, the original is only 2.5" x 3.5".
I like keeping it a painting 100% through so I had to figure out how to get super fine lines without using pens. It took over 100 ACEO to really get the hang of it. Even then, I can only do so much a day before I need to take out my contacts and give my eyes a break.
I hope she does well at auction, I really had a great time playing with the colour gradations in her hair and the background. She's pretty saucy too. LOL.