I would choose the NTSC (or PAL, if you live in PAL-land) DV Widescreen, based on that target DVD-Video.
With Still Images only, one can then let the output determine the Project.
One additional option, but the 1000 x 750 preculdes that, would be to do an HD Project, as per output to BD. Then, Export/Share that Project as a DV-AVI and Import that into a DV Widescreen Project for the DVD-Video. One would still have the BD, HD Project, should they ever wish to produce a BD.
Now, are the Still Images originally from larger files, say 4000 x 3000? If they are, I would probably go with that HD Project, re-Scale the Stills to 1920 x 1080, or very similar, and work with those. As there ARE more pixels, one consideration would be whether there are too many of the Stills for the particular computer to handle.
I always try to work with the highest def material, that I can, and then down-rez upon Export (with but a few exceptions).
To summarize, either the HD Project (with re-Scaled Stills), and then Exported/Imported into a DV Project for the DVD-Video, or just starting the DV Widescreen, and going straight to DVD-Video would be fine.