The painting you see here was created using Corel Painter 9, in an easy and fast method that uses the sketch and watercolor effect tools.
In a nutshell, this is what you do: open the photo you want to use, apply the sketch effect, copy the result, revert back to the original photo, paste the sketch on top of the photo, gel the two layers together. Easy, isn't it!
To try it yourself, start by saving this photo of the paint-splattered artist's shirt to your hard drive, then follow the step-by-step screenshots, starting with Applying the Sketch Effect. Don't worry about the fact that the photo isn't particularly sharp; it doesn't matter for this.