1.
yoh, it could be good if you remove the stolen pictures, because you aren't the artist who made it, and because stolen : it isn't good. It isn't your work, so you don't be proud about it. isn't it?
2.
For that (art thief) you can be banned from deviantart, and it could be a pity if you're banned if you're a good artist.
Be proud of your OWN art. If you like Denkikoji's art, +fav it. There is a special section in DA for that.
And if you really like his art, you can inspire yourself with his pictures.
But understand that nobody like stolen art (as somebody said before), and i don't like it.So please, remove it!
(And sorry for my english. Like a lot of people,, it isn't my language ^^ )