Originally Posted by GraciousMe
I suppoes the surefire way is to have the caption WITHIN the picture, but then my Photoshop talents are small.
That would work, but the disadvantage is that the text won't scale or follow user formatting choices. It probably won't be readable on a phone, neither will it be accessible to screen readers and such. This might not be important for your use case, but in my opinion the nice thing to do is to leave it as flowable text if at all possible, even if that results in a page break between image and byline on some readers.
Any particular reader might or might not handle "page-break-inside:avoid" gracefully, but of the currently available options I still think it's better to aim for wider compatibility if your epub is intended for general distribution. On another thread about font sizes I was advised that scaling down small parts of the text as low as 0.6em is acceptable (assuming your body font size is left at default 1em), this might help in combination with the div trick in your first post.
And yes, images in epubs are still a pain, there are no perfect solutions