Checking all URLs on a site for media?

I'm looking to scrape media from a site that has orphaned urls that looks like this:

example.com/user-d/images/[20 digit alphanumeric string ex. zxqwvl7jl745hv08yz9j].jpg

Every single non-functional url returns an S3 access denied xml while working urls have media on them. Is this just a question of brute forcing random 20 digit alphanumeric strings?