whatever you did, it was plagiarism.
like mentioned above, it's pretty simple, don't claim stuff as your own when they're not,
don't use uncredited sources for c/p, nor sources that are not a free resource..
you can't claim an idea either, like mentioned above, so if I draw a cat with a cowboy hat
that is eating purple icecream, and then you draw your interpretation of a similar idea,
then there's nothing wrong there..
however, if you take my image, and alter it in anyway, it is still my image. That includes
tracing, recoloring, replacements of sections, c/p'ing, and so forth