List header images

I know I've posted on this subject before with no site admin reply.

New list header images all turn black. I've asked if a certain size will work - no response.

But now header images that were previously fine are turning black, example:
www.listal.com/list/rachel-cook-gifs

Can this be fixed?

I realize that this is just aesthetics and the lists are "just fine" but IMO the site is so much better when "the lists" on Listal, present with a working header that someone put some thought and time into.

Yeah headers are great. With that said that list is so good it deserves a header !!!

The ability to add header images for lists was "back" for a while, but now when I attempt to add a header image the header just turns grey.