Curatescape/Omeka Image Problem

I am trying to set up a site using Curatescape and Omeka, but I can’t get my images to show up. I can upload the files just fine, but when I go to the public version of the page, the images look like the thumbnails that show up when something can’t load. This happens with the speech bubbles at the top of the page, the background image, and the thumbnail previews of files I have uploaded. What am I doing wrong?

My Omeka log-in pages says I’m running version 2.4.1, but I did try downloading Omeka 2.5 last night in an attempt to fix the problem. I transferred the files for 2.5 onto my university’s server, and deleted the 2.4.1 files, but the page still says I’m running 2.4.1. So I’m not entirely sure which version is actually running.

I’m also using the 7.0.15-0ubuntu0.16.04.2 (apache2handler) PHP and my OS is Linux 4.4.0-22-generic x86_64. Let me know if you need any other information.

Thank you for your help!