To create a rotating animation for the background image within the container without rotating the entire container, you can use a pseudo-element to apply the background image and then apply the animation to it. Here's an example:
HTML:
<section id="banner">
  <div class="banner-container">
    <div class="row">
      <div class="col text-center">
        <img src="images/BenMillerType.png" class="logo"/>
      </div>
    </div>
    <div class="row justify-content-center align-items-center">
      <div class="col-md-10">
        <p class="promo-title text-center"></p>
        <p class="promo-subtitle text-center">
          Graphic Design | 3D Design | UI/UX Design
        </p>
      </div>
    </div>
  </div>
  <div id="work"></div>
</section>
CSS:
#banner {
  margin-bottom: 100px;
  background-color: #FFFDC4;
  border-bottom: 1px solid black;
}
.banner-container {
  overflow: hidden;
  width: 100%;
  height: 95%;
  margin: 0;
  position: relative;
}
.banner-container::before {
  content: "";
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-image: url(/images/ColourWheel.png);
  background-position: center;
  background-size: contain;
  animation: rotate-bg 10s linear infinite;
  z-index: -1;
}
.promo-subtitle {
  font-size: 20px;
  background-color: rgb(42, 156, 157);
  color: #fff;
  border-radius: 30px;
  border: 1px solid black;
  padding: 10px 20px;
  position: absolute;
  bottom: 100px;
  left: 50%;
  transform: translate(-50%, -50%);
  -ms-transform: translate(-50%, -50%);
}
.logo {
  margin-top: 250px;
  object-fit: contain;
  width: 500px;
  height: auto;
  z-index: 2;
}
@keyframes rotate-bg {
  0% {
    transform: rotate(0deg);
  }
  100% {
    transform: rotate(360deg);
  }
}
In this example, we use the ::before pseudo-element to create a new element that is positioned behind the other elements inside the container. We set the background-image property to the image we want to use as the background, and we set the animation property to the rotate-bg animation we will define next. We also set z-index to -1 to ensure that this element is positioned behind the other elements inside the container.
We then define the rotate-bg animation using the @keyframes rule. In this case, we want the background image to rotate continuously, so we set the transform property to rotate(360deg) at 100% of the animation.
Finally, we position the other elements inside the container using absolute positioning, as in your original code.
This should give you a rotating animation for the background image without rotating the entire container.