I thought about this, but ultimately decided that it should be a non-factor. As it is, a team could have up to 5 different varieties of wards on the map at once, if each player chose a different skin, and if there were at least 5 different ward skins available overall.
Also, the green/pink ward confusion is also a non-factor. With the addition of the true sight eye on wards, it is very easy to distinguish between the two when you see them. Also, with current ward skins, the eye is pretty much the only thing that lets you tell one apart from the other. The model looks the same, as opposed to the regular wards with the very obvious color difference.