..: Why Can't I Use Other People's Art as "Reference" to Make My Own Art? :..
Referencing another piece of art on its own is not wrong. You may need an understanding of how a limb bends or a garment would hang/fold--it's okay to get a general idea for how tangible properties, bodies, and objects work. It's also okay to look at a body of works by a particular artist with the intent of mimicking their style for a particular piece.
It's not okay to pick up a work and "reference" the placement of essentially every element on the page, or take any one major element of that piece and say you thought of the design yourself.
Many people do not understand that all works--of any
media--are protected by an understood copyright. Intellectual property is any idea that is entirely of one's own creation; an invention is a great example. You have to file for a patent so that everyone knows who got the original rights to the royalties; but, this is to protect the money involved in producing merchandise using the invention. You don't have to file for copyright every time you make something--it's understood that you had that idea, and it's yours. The "patent" is already understood when it comes to literature, art, and film--it's rarely about money when it comes to Internet media, it's about ownership.
The establishment of this inherent copyright is the reason why Creative Commons was established--it is the exception to the unspoken rule regarding the etiquette of intellectual property. Creative Commons is a form of licensing that explicitly states how the original creator will permit others to use his work. Creative Commons is NOT the standard for any piece you find online--the inherent copyright is. You must have explicit permission from the original creator of a piece in order to use it in any way that you can claim as your own.
One makes allusions, references, homages, and parodies by mimicking the original piece. This is the only
acceptable reason and way to copy the original inspiration detail-for-detail, because the mere act of alluding to another work denounces your ownership of that idea. If you wanted to draw a picture of Sephiroth doing the pose for "The Vitruvian Man" as a parody of daVinci's original masterpiece, you would need to have the exact pose and style of composition in order for your audience to make that connection. Without these clues, your audience would not connect the two ideas you are attempting to link together. It's something akin to iconography
in its workings.
It does NOT excuse your theft just to say that "referencing" the entirety of one picture for your own picture is "an homage to the original," or that the original "inspired you" to make the exact same piece, "only different." (More on identical reproductions later.)
Regardless, adding disclaimers to your pieces are a good way to let people know what the original work(s) was. No one could ever know every piece of art in existence--and as such, it's a good idea to explain where you got your ideas. Most of your audience will probably be very interested to read what inspired your art as well--it's no admission to guilt to explain where your inspiration came from! Background on why an artist did a piece always adds depth, value, and meaning to a piece.