The most effective way to have it removed is for you yourself to file a DMCA against it, as generally third parties are usually ignored

I'm hoping the influx of reports is enough to bring in a mod's attention on the site. I don't know anything about filing a DCMA since I've never really had to do it before.

Honestly, I don't expect DeviantArt to do anything regardless of how many reports come in.
The safe way is to actually crate an account and claim the pictures as you own in there. Or just send an email of DMCA to the guys & the admins to force them.

Yeah I looked around a bit and found DA's DMCA system. I'm not too comfortable with them sharing all that personal info with the guy who stole the art. Full name, address and email.

"Upon submission, this form is sent directly to our Copyright and Etiquette Administration staff. All of the information provided in this form may be made available to the DeviantArt user responsible for the content that is the subject of the takedown notice."

If not yourself, you could design someone close to you to act as a representative of your internet persona; an informal lawyer of sorts. from there he sends his info or and relays to you the information.

It'll still ask for personal info though. I don't wanna put someone through that.