Well I'd say if someone draws an image, even if a remake, from scratch is art. It takes the talent to derive this piece even if it is a replica.
Just look at the Roman Marble replicas of Greek Bronze Statues: Notably the Severe style.
Are you going to claim those Romans were not artists?! I'd hardly imagine so.
I personally use GIMP for fun. Most of my work (Avatar and Sig), comes from images I find online. I usually then edit them with a plethora of things: Opacity, lighting, colors, contrast, etc. I don't call myself an artist, but in a sense I do create new art from an edited collage of other artworks.
I edited the Blood to look Green. Cropped out huge portions of the resurrection piece, and changed its Opacity. The main Ulquiorra is actually transparent so I had to erase anything behind it as well.
Is it an original image: yes; however, it's derived from other already established images that were then created individually by an actual artist. So I basically created a collage of three people's art that may be replicas of already made images.
Those three are artists as they had the skill to draw those, I'm not an artist, but I still made something that's artistic.
For example, my Avatar contains a collage of three photos: Ulquiorra, Ulquiorra in his resurrection, and a Blood drip image.