I prefer PNG over gerber personally.
As long as it is not a crappy screenshot that has a bad resolution, it does not matter if they use PNG, PDF or gerber. What matters is the reviewability.
Maybe in the FAQ or guidelines can point them to this: https://www.reddit.com/r/AskElectronics/wiki/design/#wiki_schematic_diagram_guidelines
This is a nice one, but on a quick glance I partially disagree with the bit on the power supply symbols. It should be a balance between the amount of them. Take for instance the schematic iterations found in this thread:
https://www.eevblog.com/forum/beginners/advice-on-my-first-larger-design-in-kicad/?topicseenAttached are parts of it showing what I mean. For me the second version is better, but for my taste the power and ground symbols should be on the left and not in the middle.
In my eyes there are many problems with that schematic that do not require that much effort to make them more readable. Like on that page with the power supply bits, instead of those three blobs that have close interaction, draw it as one single circuit without those supply symbols all over the place.
How would a child board for "crappy" material help? We seem to have enough boards already, much less child boards, including one for political and personal attacks misleadingly named "General Technical Chat."
It would hopefully save us from having to point out the rules for how to draw a proper schematic every time some noob or wannabe posts one to have it reviewed. Maybe just a sticky at the top of the beginners section, but that would not be read if they post in the projects section. Sure a dedicated board might still be missed and the sticky in it can also be skipped, but if it only set a few people straight on correct schematic drawing that would be a win.
With the internet full of those shitty youtube videos and all those crap dev board schematics the Chinese are throwing at us, it is only getting worse. So who knows if our effort will help in balancing it a bit.
And I know I can just ignore and skip all that crap, but what would the forum be without people willing to put some time in helping others.