Custom UI icons - what are they?

[MikeBlyth]

I'm just trying out the custom UI. The docs refer to an icon defined by a string value. What is this icon? An object in the game? A bitmap? Is the string value supposed to be the UID or what? I can't find this in the documentation, probably just haven't looked in the right place.

[LordAshes]

I found this in the documentation. Not sure if it is related:

Image Attributes
Applies to elements with an image component. The string that images all take is the NAME THE IMAGE WAS GIVEN WHEN YOU PUT IT IN THE IN-GAME ASSET MANAGER.

What is the IN-GAME ASSET MANAGER? Is this the CLOUD MANAGER or do we need to load these assets in using code like:

function onLoad()
    local assets = {
        {
            name = "Image 1",
            url  = "http://placehold.it/120x120&text=image1"
        },
        {
            name = "Image 2",
            url  = "http://placehold.it/120x120&text=image2"
        },
    }
    UI.setCustomAssets(assets)
end