Composition
One trick I use to test the composition of a scene is "paintovers”. I take an image into Photoshop and extend/crop the canvas size, twist it, paint new elements, change colors, etc. It is a quick and dirty method to preview changes. If I like them, I recreate them in 3D.
Fig.18 is one of those tests. In this one I took some decisions, like placing an ashtray near the character and a few framed paintings on the back. I decided to flip the image horizontally because it worked better that way – we read it from left to right. I also added a slight tilt to make the composition less static. The rabbit's eyes are at a one-third distance from the top and from the right side, in order to become the center of our attention.
In the final composition (Fig.19) I had some trouble making sure the Mona Lisa did not compete with the rabbit in terms of attention. For that I had to let the rabbit's ear slightly overlap Mona Lisa's frame, so that it became obvious that the painting was behind the rabbit. I also intentionally left Mona Lisa's eyes out of the picture to avoid having two pairs of eyes fighting for the viewer's attention.

Fig. 18

Fig. 19
Compositing
Photoshop was used for all the compositing. I had already done a lot of lighting and material tests in 3ds Max, and as such I didn't find it necessary to create render passes to fine-tune the lighting, reflections, etc. further.
I rendered three separate hair passes – body, snout, and tail – by setting the Composite Method to None in the Effects > Hair and Fur window. I rendered the base image with the hair shadows but without the hair by setting the Composite Method to Off in the Effects > Hair and Fur window. A ZDepth pass was also rendered and used to defocus the background with the Lens Blur filter in Photoshop. In addition to this I rendered an Occlusion pass using Mental Ray, which I consider to have a far superior occlusion shader comparing to VRay's dirt shader (Fig.20).
To finalize the image, I painted some dirt marks on the wall and on the floor, painted the smoke in the air and coming out of the cigarette, and added more light from the top right corner by painting over the image with the Color Dodge blending mode.

Fig. 20
Conclusion
The technical aspects of a piece are important, but what really matters is the reaction it provokes on the viewer. I like humorous images that make people smile. That was the main goal of this piece. I also introduced some secondary comic elements on the image, like the smoking Mona Lisa and the carrot earring, because it's fun for the viewer to discover the jokes as they explore the image.
I am very happy with the way the final image turned out (Fig.21). I hope you have enjoyed this article as much as I have enjoyed writing it for you. Thanks for reading!
Fig.21