The majority of shots throughout the animation will be rendered in 3D, however they need to retain the impression that they are 3D realisations of a 2D image. I've found that the Toon shading settings in Maya do a pretty good job of accurately emulating Fahima's style.
To achieve the effect, I assigned shaders that change in response to the angle of the light. This allows me to have objects with colours that dynamically alternate on each side, similar to the buildings in the painting.
Colours Rendered in Mental Ray
I then assigned outlines to the objects as Paint Effects, using a custom brush to emulate the brush strokes in the painting.
Outlines Rendered in Maya Software
The colours are then rendered out in Mental Ray and the outlines in Maya Software, after which they are composited together in Photoshop (or After Effects when rendered as animation).
Colours and Outlines Composited in Photoshop
To give the impression that the image has been created using the same materials in the painting, I have tested two different methods. The first was entirely in Photoshop, using a brush stroke and a newspaper texture, with overlay and multiply blending modes. I feel this method does a better job at sustaining the illusion of a painting than the second method.
Paint and Newspaper Effect as Overlays in Photoshop
The second method is using the Light Angle Two Tone shader, with two textures assigned to two ends of a Ramp. One for lighter areas and one for darker. This method produces an image that, whilst visually appealing, isn't as faithful stylistically as the preceding technique.
Paint and Newspaper Effect as Textures in Maya (One Object Only)
With some refinement, this looks like a promising route to go down. It sells the style effectively and is fairly simple to execute. I think the next step is to highlight some of the more unique elements of Fahima's style and find a way of incorporating them in the render, hopefully resulting in a far more convincing outcome.