Agree. DynamoDB + S3 seems like a good choice from my side. S3 will store the data - whether it is images or videos. DynamoDB can store the metadata associated with which museum uploaded the file, what date, type etc. NoSQL suits the dynamic nature of content which you are storing. You can build a website on top of it to support whatever you want.

Also a simple dropbox may also work if the goal is just to aggregate information and nothing else.

All depends on what you want to do with the data.