Here's a commissioned one-off watercolour portrait card that I completed last month. I was given a photo of the girl in question jumping in front of a fountain somewhere in Europe to use as a base. The client wanted enough of the background remaining for the original location to recognisable to the recipient, so I left in the fountain and added a few trees. I also enlarged the girl quite a lot from the original photo, to make her the focus of the card.
It was a difficult format to work from, to fit in a jumping girl and the fountain in the space of a standard ratio greeting card. I would have preferred a longer format so I could have more space below her, but I didn't have an envelope that size. If this was an illustration I would have done things a bit differently, but for a portrait from a specific photo, I kept everything as close to the original as possible. I altered all the colours from the winter photo - from blacks and khakis to more pastel colours - to work with the birthday theme and added some spatters and metallic paint to give the whole thing more fun and energy, along with flicking out the hair and jacket and other artistic-license tweaks. =)
Four hours using Copic Multiliners, Winsor and Newton watercolours and metallic gold Ecoline on Moleskine watercolour paper.