There are various issues regarding the top row decisions. Note that I am not an administrator neither I try to take side in each occasion, my scope is to remain objective from a neutral standpoint.
A. The top row serves only as a decoration element and not as an authority of deciding the fate of each artist’s work. So in either case a work is featured only as means of decorating the website.
B. There are some elements that make original work somehow better than copyrighted. Using copyrighted material as a basis of a work is a very delicate subject that needs care and consideration because it hides lots of surprises and troubles behind it. At very best the works based on copyrighted material will be considered as “fan art” which is the opposite of “professional art”, and this is only for the conceptual part.
C. Also in many cases works that include characters, might be considered somehow better because it will “liven up”, in comparison for example to works such as architecture or vehicles that seem a bit “cold”. As themes that contain not living elements have this “moody coldness”, because you know, they are objects. In this occasion perhaps only the rendering elements can be extracted, but this would require the mind of an expert with extraordinaire de-composition skills. But for the simple visitors and the persons with standard art-intelligence, they would look for more emotional cues in a picture.
D. Also there is the aspect of non verbal communication and what emotions the work produces, for example characters that are well designed or pleasing to watch will have other effect, in comparison to other characters with “specific-not-so-well-designed-features”. This has to do psychology mostly and the social standards are set. This does not apply to characters only, but in houses or vehicles. For example if you have an old house with rust and dirt the mood will be heavy and the work will communicate in other ways than the one that is supposed to. On the other hand if you have a shiny and brand new house - WYSIWYG - which makes things very simple to interpret the image.