Susannah and Mia

I am a big fan of Stephen King's Dark Tower and this is actually the first fanart I've drawn of it. This is from the sixth volume ("Susannah's song") and, as the title already implies, portrays Susannah, the divided girl, and her possessor Mia in "Mia's Dogan" on the Discordia side of the castle.
First I inked the rough sketch and then shaded the background with a graphite pen. Lastly, I coloured the characters using watercolours. Though I do think I should have left the background last because it was quite hard to try not to mess it when I coloured the characters, but I was scared to proceed to colouring, because that's the most important part of a picture and I often mess it up. So this is how it turned out. I'm not exactly proud of it (it's not my best work) but it's not bad.
Can't wait to get the last part of DT to my hands. I should get it next week when it's my birthday!