The difference between getting inspiration from a piece and and stealing an idea is that when you steal an idea you are almost exactly copying what someone else has done. When you get inspiration from somebody you are using their idea to make your own idea.
Yes, 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. As long as you are not just exactly copying another persons work, it is okay to use their ideas to create something of your own.
Yes, 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. As long as you are not just exactly copying another persons work, it is okay to use their ideas to create something of your own.