It seems feasible to me that a script could be written that allows screenshots to be inserted into an existing PND (extract/mount, add screenshots, modify PXML, repackage), if this was the case, it might convince maintainers to quickly repackage the PND up. Much higher chance than if they need to locate source, get their build environment fixed back up, find out something doesn't work right, etc. It is also nice to have everything embedded into the PND as when you download it, the screenshots can be shown in preview panels of launchers etc.
If you wanted to be forceful, the repo could reject PNDs that do not have embedded screenshots, but that possibly crosses the line of being ungrateful (hey dev, you may have spent 6 months painstakingly making a great new game for us, but if you don't follow our rules we don't want your work!) on the flip side, if a dev is spending time to make a PND, adding screenshots really isn't much work, and does make it more likely that more people will see the title. Do we know how many PNDs are currently on the repo with no preview pictures vs ones that do?
Hmmm, more questions than answers from me
