So I was just sent this. Thought y’all might wanna take a looksie.
Every image host has something like this in their Terms of Service.
Here’s that of Imgur, a popular image host:
With regard to any file or content you upload to the public portions of our site, you grant Imgur a non-exclusive, royalty-free, perpetual, irrevocable worldwide license (with sublicense and assignment rights) to use, to display online and in any present or future media, to create derivative works of, to allow downloads of, and/or distribute any such file or content.
Here’s that of DeviantART:
For the sole purpose of enabling us to make your Content available through the Service, you grant to DeviantArt a non-exclusive, royalty-free license to reproduce, distribute, re-format, store, prepare derivative works based on, and publicly display and perform Your Content.
Facebook’s:
For content that is covered by intellectual property rights, like photos and videos (IP content), you specifically give us the following permission, subject to your privacy and application settings: you grant us a non-exclusive, transferable, sub-licensable, royalty-free, worldwide license to use any IP content that you post on or in connection with Facebook (IP License).
Twitter:
By submitting, posting or displaying Content on or through the Services, you grant us a worldwide, non-exclusive, royalty-free license (with the right to sublicense) to use, copy, reproduce, process, adapt, modify, publish, transmit, display and distribute such Content in any and all media or distribution methods (now known or later developed).
Incidentally, this is the text right above it:
You retain your rights to any Content you submit, post or display on or through the Services. What’s yours is yours — you own your Content (and your photos and videos are part of the Content).
And yes, Tumblr too:
When you provide Subscriber Content to Tumblr through the Services, you grant Tumblr a non-exclusive, worldwide, royalty-free, sublicensable, transferable right and license to use, host, store, cache, reproduce, publish, display (publicly or otherwise), perform (publicly or otherwise), distribute, transmit, modify, adapt (including, without limitation, in order to conform it to the requirements of any networks, devices, services, or media through which the Services are available), and create derivative works of, such Subscriber Content.
Tumblr’s ToS, however, also explains why you’re granting them these rights:
The rights you grant in this license are for the limited purposes of allowing Tumblr to operate the Services in accordance with their functionality, improve the Services, and develop new Services. The reference in this license to “creat[ing] derivative works” is not intended to give Tumblr a right to make substantive editorial changes or derivations, but does, for example, enable reblogging, which allows Tumblr Subscribers to redistribute Subscriber Content from one Tumblr blog to another in a manner that allows them to add their own text or other Content before or after your Subscriber Content.
In order for a service (like Tumblr, or Discord, or Facebook, and so on) to be able to do something as simple as showing a picture you uploaded, it needs to cover several steps: hosting pictures on their server, generating and displaying thumbnails, allowing them to be shared, retweeted or reblogged, and for it to be visible regardless of where you’re located in the world, or anyone else who might see it - and they need these permissions for every one of these steps (and maybe more), or they would be in violation of copyright laws every time you upload something.