If you're going to post fanart of Pterano that you didn't draw yourself, it would be a good idea to credit the name of the artist in the video descriptions. Not all artists would be happy with the idea of their art being posted without even being credited. And other still would want to be asked first before their art is used.
And to answer your question in the first video, of the sketches of Pterano, those were drawn by a friend of mine, Delete_Lover.