My guess is your CSS class should be .sheet-container from the character sheet wiki CSS/Styling You can use custom CSS to style the way that your sheet looks to players. You can use nearly any CSS styling that you want, including background images, colors, font sizes, etc. There are just a few caveats to note: All of your CSS styles will be restricted to the ".charsheet" parent class. So if you put a style called "input", the system will automatically prefix that with ".charsheet input". This shouldn't affect you in general, but it prevents you from changing any of the Roll20 application CSS outside of the character sheets. Note that by default, any HTML classes defined in your HTML layout which don't begin with "attr_", "roll_" or "repeating_" will be prefixed with "sheet-". So for example, if you want to style some of your input tags to be shorter than others and you define the HTML as "<input class='shortfield'>", when processing your layout it will be changed to "<input class='sheet-shortfield'>". So basically, you should probably prefix your classes in your HTML and CSS with "sheet-" to avoid confusion. Not sure that's all that needs to be fixed, but that would be a quick potential fix. :)
