What makes a good image target and how will we know that it will track well? We can identify characteristics of the physical target and the image on it.
The target itself should have a matt finish to avoid reflections and specular highlights that might confuse the recognition software when it's processing the video feed at runtime.
It also should be rigid so it won't be distorted or morphed when the camera is viewing it. Thus, a card or paper board won't be able to bend or crease as easily as a regular piece of paper. The tracking will be more consistent.
The image should have a border so it can be readily distinguished from the background. The recommendation is this border should be roughly 8% of the image size. The border can be just white around the perimeter. Or it can be part of a texture. But just keep in mind that 8% from the border will not be taking that pattern into account.
Given these requirements, or shall we say guidelines, an ordinary business card...