I started out with having an idea that I should always show a random image when clicking on the "Show me another one!" button. However, I quickly ran into problems when people would see repeated posts as the MySQL RAND() function might return repeating post ids. Creating a more complicated algorithm to save all the posts in a cache that had already been viewed and also saved in a cookie created some unnecessary complexity. In the end, I ended up just showing the last posted image and the button basically takes you to the previous post every time you click it (or tap if using a touch device).
I used Import.io to write a crawler API to fetch the top posts. Then I wrote some cron jobs to automate calling the API to fetch the latest posts every three hours. The actual job runs via a beanstalkd queue as a Laravel artisan command.
I didn't want to hotlink the images directly from Imgur as I didn't want to leech on their bandwidth, so I used Cloudinary to display the pictures instead. One advantage was that with the Cloudinary API, I could resize the images and/or convert gifs to an MP4 on the fly (MP4 files take a lot less bandwidth to deliver). However, since I am not making any money from the site and wanted to stay on the free plan, I decided to mostly ignore gif files as they take a lot of bandwidth and disk space on Cloudinary. The Laravel queued command also takes care of uploading the images to Cloudinary.