Many articles on this Wiki have images whose captions end in a period even when the caption is a short description or is a sentence fragment. However, most modern publication styles do not use captions in such situations.
For example, Wikipedia's manual of style states that:
- "Most captions are not complete sentences, but merely sentence fragments, which should not end with a period. If any complete sentence occurs in a caption, then all sentences, and any sentence fragments, in that caption should end with a period."
- "The Conservatory during Macquarie Night Lights, a summer festival" (no final period), but
- "The Conservatory during Macquarie Night Lights. The Conservatory was spotlit for the occasion." (final period for complete sentence and another to conclude the preceding sentence fragment)
https://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style/Captions#Formatting_and_punctuation
That is, according to the above style widely used in Wikipedia, periods are used only if there is a complete sentence, or if there are multiple separate sentence fragments.
So, I suggest we adopt the above style guideline for purposes of consistency.