You cannot use work that isn't yours without the artists permission. Please remove any/all other deviations that you did not make COMPLETLY yourself , or they well be reported. And I mean ALL of them. I will check. If it is reported, your artwork will eventually be forcibly taken down by the staff, and you may be banned.
"Other people do it", "Don't like, don't look!", "You're not dA staff!", and "Why aren't you telling OTHER people this?" are not excuses to break the rules, I'm afraid. I understand that you may not be able to contact the original artist, and that is exactly why you cannot upload this. Nor is this protected under Fair Use, as dA copyrights your work for you (and it is against the TOS anyway.)
Please note, I am not dA staff. This is also only meant to be a friendly warning, so you won't get into trouble (I haven't reported this yet). I do not post this with the intention of trolling or harassing you. However, if you hide/flag this comment, and/or block me without expressly stating that you will remove the deviations in question, I will assume you won't be taking them down and instantly report you.