Amazon customer uploaded images...are they safe to use?

I assume you mean to sell the products, and not just for
editorial/news purposes.

Amazon does not hold the rights to those. They don't even
hold the rights to the images they use. They have agreements
with publishers, celebrities, etc.

When you signed up to be an associate, you agreed to only
link using the terms of the agreement. Probably many, many
people break the rules. Amazon probably is not as militant
as google. You are not even supposed to mask links in any way,
even using a link shortener.

In plain English, I suppose, they want the stuff you use to
make known upfront that you are an amazon affiliate, and all
links go to amazon.

You are operating under the license granted to amazon to follow
their rules. The catch-all is:
" Unsuitable sites include those that: otherwise violate intellectual property rights. "

Now the kicker, is that you can share the images via social media. How
one could incorporate a sales pitch with amazon links is up to you.
I can probably think of ways, but is that the same as what you are
asking? Don't know. Maybe you can come up with something.

Paul