Currently, imgblock tags embed the description provided in the image itself as a caption, and provide no means of entering a custom context-based caption instead. I propose adding an additional option to the imgblock bbcode to allow providing custom caption/description information.
This would allow imgblock tags to have captions that are context appropriate to the article or section of an article they're being placed in - I.e., a blurb pointing out the part of a piece of artwork relevant to the text around it, as opposed to the generalized description that appears when viewing the image directly.
Formatting could probably be done with \Custom caption here\[/imgblock\] and render something out like the following, perhaps with support for bbcode being entered within the custom caption.
https://i.imgur.com/GeR9VO8.pngI was about to raise a feature request for this exact thing :) I want to be able to write descriptions with the rest of the paragraph wrapping under it as they do with the credits, but it is impossible (to my knowledge) if it is not part of the credits themselves.