I'm a bit at loss, when looking at source, there are some indications that cloudflare are involved in the display of the page, so would seem it may be their end, but hard to know for sure as I'm not really familiar with cloudflare myself.
First I thought it could be something generated by the script you use, but it definitely looks like a normal index of, except for the bottom part which does look more like a part of a page with the text about public domain icons.
The icons folder, is that something you recently added, or has it been there from the start and working before? If the former it could be my theory is correct and it just clashes with some internal parts of the script in use, otherwise it is an interesting but annoying issue.