I really think it's a pretty simple answer. To me, if the process in which it was done is pretty transparent, and artist isn't taking credit for someone else's art, it's ok. In this case, these type of tools can make whatever they want, however complicated they want, but the main point is in the end, does it truly have all the needed traits for great quality pixel art(or the media/style of art in question), and was it all done by the artist him or herself. When dealing with submissions, these are the things that are most important to me. I never much liked when artists used existing works, edited them, and called it their own; I think that is what most artists can't stand, whether it pertains to their favorite type of media, or not.