This was a hard question to answer...I love them all! I did eventually choose Thrackerzod though, namely because the line, "I WANT TO BE AN OOMPA LOOMPA! take me to them so the Deed may be Done..." never fails to make me laugh. That said, I love both the design and personalities of all of them.
Beyond her appearance in Biker Gorilla and Enunciation Emergency, the images of Aurora that you and others have done have caused me to like that character even more...And what's more, DeMarcus does a wonderful job with her voice (Actually, that can be said with all the FimFlamFilosophy voice actors...)
So...Basically, although Aurora and Orion were characters made for Biker Gorilla/Rainbow Factory, I do hope we will get to see them again!