Hi,
See my portfolio for example of form, which you need.
I had made form, that display image files as a large thumbnail (size of them can be changed - they can be less or more).
If there are multiple images then they are all displayed as large thumbnails.
If you select any image in form, then it will be shown on the right side of the form.
If you double click on image, then it will be opened by default browser.
Regards,
programmer Aleks