It works \o/
Screencast attached in ogg format, should just work on Ubuntu, if you are using something else you might need to use VLC to play it.

It uses jquery to show and hide the text and images, all the images are assets within the application and a placeholder div is provided in which the buttons place the assets. I wrote a little helper function to translate asset names to uuid references to get the images and load them into the div based on a json array of data that comes from the server when you are logged in. The interesting functions are the one that converts and asset name to an asset ID

function aid(assetname){
    for (var key in assets.assets) {
        if (assets.assets.hasOwnProperty(key)) {
            if (assets.assets[key].name==assetname){
                return(assets.assets[key].uuid)
            }
        }
    }
}

function showsign(){
    $("#BSLletter").hide("slow")
    signuuid=aid("sign"+letter)
    $("#BSLimage").html("<center><img src=\"/media/assets/"+signuuid+".png"+"\"></centre>")
    $("#BSLimage").show("slow")
}

just for reference, attached here are the bits of code that do the magic, assets.js is mostly the content of http://maker.spotspecific.com/E/ALC/assets/ which is a json manifest of all the user's assets.

Hey Alan,
Wow, that's a great idea for an app. Looks like it's working well too. I'll feedback your helper function to the development team and see if we can get a more helpful API method in there for you.

Thanks,

Graeme West

Spot Specific Community Manager

I am missing a good way to showcase apps. I uploaded the screencast to youtube http://www.youtube.com/watch?v=4QQ1DnoC_jM (which was a bit of a pain as I had to re-encode with ffmpeg as apparently youtube don't accept ogg files for some reason. Ideally what I would like to do is press a button in the UI to say my app is ready for public view which would allow anonymous access to the web preview URL, which could then be embedded in an iframe in this forum, or in a blog or wherever so other people could preview it and provide feedback to improve it prior to submission to iTunes and Android stores.