Oh, is it! Sorry, I'd never heard of it. Ha, shows what I know. :) But that just means that your icons will be hosted on Weebly, using the webspace they give you. If your icons are, like, super mature or whatever, you might want to check their ToS just to make sure it won't get booted without notice.
From what I can see on the website, it looks like there's a pretty easy way to build picture galleries through drag-and-drop, so maybe that's your best bet.