Disembodied limbs are usually people/characters too (check the related wiki articles for more details):

• disembodied_hand - each hand could belong to a different character, or a pair of hands could be from the same character. Rely on scene context and thumb orientation to determine this.
• disembodied_penis - each penis likely belongs to a different character (multipenis/hemipenes not withstanding).
• disembodied_head - each head is likely a different character, unless the disembodied head and headless body are the same character

Select Multi-image if multiple images are present and you're not sure how else to tag it.
Model Sheet is a possible option due to the model's genitalia often being showcased (this is still solo).

Note: the two/three/four+ options also include solo_focus, this is likely to be the case most of the time that disembodied limbs + multiple characters are involved, but occasionally may not be.