You can scale the image to fill the Edit Mode monitor space provided by the setting of the project preset 16:9.
You can use PAL DV Standard instead of PAL DV Widescreen for the project preset
You could crop 16:9 then resize your photos before import into Premiere Elements with the PAL DV Widescreen project preset.
I do not understand your description of your photos, assumed jpg stills. Where are you getting the video pixel aspect ratio of PAL DV Standard 1.0940 for stills jpg? The pixel aspect ratio = 1.0940 is a non square pixels to square pixels correction factor for PAL DV Standard (video).
Thanks again for getting back to me.
I got the Pixel Aspect ratio of 1.0940 by right-clicking on a jpg on the Timeline and selecting 'Show Properties' at the bottom of the drop-down menu.
OK, I abandoned the above project and gave my new widescreen project the same Preset values (please see screenshot)
except that this time I turned on the Default Scale to Frame Size option in Edit Menu/Preferences/General. Then I imported my images (the same 720 x 576px images) onto the Timeline. The two black sidebars still appeared down the left and right-hand sides.
So, I abandoned that project.
Now I have opened up a new project, PAL DV Standard (screenshot):
I have also turn on the Default Scale to Frame Size option in Edit Menu/Preferences/General. I have imported the images to the Timeline and this time - hooray! - the image fits in the monitor/editor with no black sidebars. (This is what I wanted to achieve with widescreen.)
What I now need to do is allocate a time, let's say 5 seconds, for when each image is visible onscreen plus add a transition, probably a 1-second 'Cross Dissolve' between each image. In order to allocate that time of 5 seconds for the appearance of each image, how do I determine that amount of time (keyframes?) and, after doing so, would you then select Transitions | Dissolve | Cross Dissolve and add the transition that way?