I was trying to do the same thing. Add a image carousel in the footer to make a logo slider. Since this function was not available, I did a work around...
I made my image carousel just in the page, with all the right settings and CSS. Then I opened the pages code in Google Chrome, searched for the section and I copied the entire thing. Then I added a code block in footer and paste the code their. It works and it's mobile friendly. There are some beauty troubles tho like page width and white space between the sections but yeah..
I've hidden the "donor" section on the copywriting page where I copied the code from. So when I want to add or edit the logo wall I just do it there, then refresh and copy/paste the code again. It's a big work around, but it beats editing almost every page when we add a new big client or project which we want to show off in the logo wall.
You can check out the site www.alphaleads.eu. Hope this helps, and hope that @Squarespace will add the function since this is just basic CMS I think. Making a "template" like a logo wall which you can edit when you want and paste in pages you want.