The material itself is copyrighted. If the similarity is too high, it may cause infringement. However, it is not necessarily true that many pictures on the Internet (the quality of the pictures is not very high, and they are sold on non-material websites) generally do not constitute infringement, not to mention the pictures of flames you use, let alone what infringement does not. In terms of materials, only portraits, trademarks, etc. are the most likely to constitute infringement, and the rest of the elements, when you are design elements, will not cause much infringement.