It sounds like the things you want to do are outside of the scope of ChoiceScript, though I admit I don’t understand what you want regarding “a *percent health where the stat buttons are.” Do you mean that you don’t want a “Show Stats” button, but would rather have a permanent display of a health bar? If that’s what you want, you’ll have to edit the index.html file to display what you want using HTML and possibly CSS, and then write some JavaScript to update it when it changes. To call your custom JavaScript code, you’d use the *script command in ChoiceScript. If you write custom HTML/CSS/JavaScript, you can make the health bar look any way you want, within your ability to write the required code.
If you do something custom like that, don’t expect it to work for a native Kindle app. I don’t know about the other mobile devices.
There is a simple way to get a background image for your ChoiceScript game on the web; again, this won’t work for a native app on the Kindle, and I don’t know about other mobile devices. For a web-based ChoiceScript game, you can use CSS in your index.html file for this. In the head of the index.html file, to get a background image for the entire page, try something like this:
<style type="text/css">body {background-image: url(<em>URL-of-your-image-file</em>);}</style>