Perhaps someone would like to know, although no one answered.
There is currently no Photo Gallery dialog box (although it has been announced and is likely to be released in an update in the near future). Nevertheless, you can call the dialog for selecting your own file from another stream. For more information about this, head over to the Cascades support forums and find a topic called "Using the built-in file and file browsing dialog in Cascades."
Here's a link .
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