About the download buttons you can read
http://www.remark-webdesign.nl/page/extra-lay-out-through-pivotx-buttons/remarkwebdesignen.
You will see that a download icon is shown (icon_image.gif is used from pivotx/pics for .jpg).
The download is executed but the browser then kicks in. If it is a known extension the image is shown like you would have selected 'Show image'.
Compare this behaviour with the pdf download (try the example on my demo page): the browser will also kick in if you have a pdf viewer installed.
As far as I know you cannot circumvent this behaviour except just use an extension that does not have browser behaviour attached to it (like the last download sample with extension .xyz).
If you use parm icon with value icon PivotX tries to find a suitable icon for you (see module_smarty around line 2325) based on the extension.
Does this help?
Quality is in the detail of things............
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