3
I think:
"thickbox image" is the original uploaded image
"screenshot image" is resized as thumbnail only if, in module preferences, "Use Thumbnails" preference is setted to "Yes"
In templates files, for example in "wfdownloads_singlefile.html":
"thickbox image" url is <{$xoops_url}>/<{$shots_dir}>/<{$down.screenshot_full}>
and it isn't resized
"screenshot image" url is <{$down.screenshot_thumb}>
and it is resized according to module preferences