Nice! Will try it out later.
Do you mind reducing the quality of the 5MB and 2MB images? About 1MB max. would be sufficient. Maybe even lower than that would look good. This does end up bundled in the app, so it will increase the app size.

Could be nice to add a very discreet credit to the original creator of each image/screenshot - a simple semi transparent overlay div in the top/bottom right of the image would probably do nicely? Could just create a new corresponding array with author names for simplicity, or change the array to a key/value object with filename and author values for future flexibility?

This is a good idea! (If they want to be credited, of course). Though I think for lot pics the lot name and creator should also be credited. For example:

John's Lot – Strangetown
Picture by Jane

If the picture is just Sims having fun, just the "Picture by Jane" would suffice.

Bottom right of the installer backdrop seems like an appropriate place for this:

Yeah I’ll compress the images, bearing in mind these images are just placeholders until I gather some better ones. Can probably get away with an even smaller filesize than 1MB without much loss of quality.

I was thinking there for the credits, too. Perfect.

The lot name credits sounds good to me. And if on the rare occasion someone does not want to be credited, can just hide the div when that slide is showing if the corresponding credits string is null or “”?

Had no offers of screenshots on Discord yet, may have to go out taking snaps myself but would be nice to have some good screenshots of a range previous events etc, which I don’t have.