The other big issue here is copyright. Basically, all outreach presentations will have images whose copyright is owned by the original observers. Your average local society will typically operate on the basis that nobody is going to complain about their images appearing in a talk – but as soon as you start distributing the slides online, you are redistributing people’s work and clearly need consent to do that. Within the BAA this is managed through our T&Cs, which say that any images submitted to sections or online can be reproduced in any BAA publications, but that does not extend to inviting local societies to edit and reuse the images and share them online.
Sorry if that all sounds very negative!
A possibility might be to see if any of the Creative Commons terms and conditions are usable and, if so, insist that an appropriate copyright notice be attached to the material in question before the BAA would host it.
Agreed, copyright can be a minefield with the mines laid in a swamp.