
Reliable Long-term Image Hosting Sites That Will Stand the Test of Time

This is a list of reliable image hosts with a good track record and more than a few years under the belt. All image hosts on this list support hotlinking.
Imgur will not be listed here since it's gradually turning worse in its quest to transcend from a mere image host into a social network. For example, direct links to Imgur images redirect to the image post's page on mobile instead of the image itself nowadays so that it can show ads, get visitors to click on trending images in the sidebar, and interact with the community via the comment section of images.
Discord is a text, voice, and video chat software that is particularly popular in the gaming community. Users are able to create their own servers within Discord where they create channels. Discord also has excellent built-in image hosting. Images hosted on Discord are there until you delete them. The fact that Discord has over 45 million users, are gaining 1.1 million new users per week, have a $4.99/month premium plan called Nitro and has gotten over $79.3 million since 2012 in venture capital and seed funding suggests that they should be able to pay their hosting bills for the foreseeable future. The maximum file size per image for free users is 8 MB and 50 MB for paid Nitro users.
Postimage is a veteran image host with a beautiful interface that has been online since 2004. There was a time between October and November of 2016 when PostImage was close to having to shut down due to gigantic hosting costs, but they managed to solve it quite nicely within five days with the help of the community and it doesn't look like they are going anywhere anytime soon now. As for file size limits it allows free users to upload images up to 12 MB and 10 000 x 10 000px in resolution. Premium users have a higher file size limit, which is 24 MB.
Imgbox is a great image host with 10 MB file size limit/image, album functionality, and comment fields. It has been online since 2010. There was a time in June 2017 when Imgbox was set to shut down because the site became too big for their previous hosting platform to handle. However, they managed to partner with a new team that has a lot of experience with large-scale hosting and in the end never had to shut down. This is the website on the list that shares most of Imgur's functionality, so if you're looking for a image host that feels like Imgur but doesn't compress images, this is the one. (Imgbox is however just an image host, not a social network like Imgur, so don't expect the comment sections to be anything like it or even active.)
Gyazo is a software that launched back in 2009 and lets you take screenshots and upload it to their website where it will be stored "for the forseeable future". Gyazo also has two premium plans, which should mean that they have the capital needed to back up that claim. They do not however support uploading images that are not screenshots taken using their software.