SBOMs may be an important short-term use-case, but ultimately the spec will now provide a "blessed" way to attach even a cat picture. It can be uploaded standalone or pointing to a container image.
The way to indicate a non-container artifact type is to use the "artifactType" field. Your client may choose whether or not to support older <=v1.0 registries by falling back to use "config.mediaType". The way to attach the artifact to the image is to use the "subject" field, pointing "subject.digest" to the proper digest of the thing you're pointing to (e.g. "sha256:..." ). There are no limitations there either, you may point cat pictures to cat pictures.
The way to indicate a non-container artifact type is to use the "artifactType" field. Your client may choose whether or not to support older <=v1.0 registries by falling back to use "config.mediaType". The way to attach the artifact to the image is to use the "subject" field, pointing "subject.digest" to the proper digest of the thing you're pointing to (e.g. "sha256:..." ). There are no limitations there either, you may point cat pictures to cat pictures.