There is definitely a difference between being inspired by someone's work, and stealing someone's work. When an artist steals another's idea, and doesn't not implement his own ideas, the thieving artist is in no way being original. The ladder, being inspired, is when an artist technically steals another artists idea, but implements his own ideas to make it his own.
It is okay to use part of an idea or part of another picture in your piece if you change something or give credit to the original source. This is only acceptable if your whole piece is not just someone else's work.
For my final piece I combined a compass and an eye. I chose these two items to combine because when I look at an eye it reminds me of a compass so it was easy to combine the two.
I picked the medium I did, watercolor, not because I like working with it, but because it matched my idea because eyes have tons of blending colors and swirls in the iris and it is easy to blend watercolor.
The most successful part about my piece, in my opinion, is the iris. This is because I picked a very nice purple and made two different shades of it which gave the iris dimension.