Can I set custom HTML elements to be added by SiteCake?

editing
#1

An example:
I am a web developer and I use SiteCake to let my costumers edit their websites by themselves.
One of my costumers’ website has a gallery in it, whose items are in this format:

  • SomeAlt

    • Can I add this HTML structure as a custom element to sitecake, so my costumer can add new items to the gallery without having any HTML knowledge?

    #2

    Edit: Apparently my HTML structure example was interpreted as a real HTML structure. I’m new here, and I’m kinda lost, sorry.
    The structure actually is:

    <li class="gallery-item">
    <img src="SomeImg.jpg" alt="SomeAlt">
</li>