The image-picker macro displays an interactive image picker, as can be seen in the core text editor.
imageTitlecontains the title of the tiddler containing the selected image.
The images are selected by means of a filter expression, into which the
subfilter parameter is spliced as follows:
[all[shadows+tiddlers]is[image]$subfilter$!has[draft.of]] -[type[application/pdf]] +[sort[title]]