BTW, I would recommend to add a further option to the "image" button, which is "slide show", and that would result in presenting this FORM with two or three FIELDs in a loop until the user clicks on a "Done" button in this field.

And to create a HTML markup of this slide show as an unnumbered list UL with a CSS of {list-style-type: none;}, the LI with {float: left;}, and in the LI the A encloseing the IMG with {display: block;}. The caption/description to the IMG should be enclosed in the HTLM5 tag <FIGCAPTION></FIGCAPTION> (ignored by non-HTML5-aware browsers), and the IMG and the caption between the <LI> and </LI> with <FIGURE> and </FIGURE>

The BB-code would just change to an IMG=lighbox-showID and have one added parameter, namely a TITLE= with the text the user has entered as the caption/description of her/his image.