Wootah A seperate layout for your pause screen may not be as good of an idea, but if you do want to store some info, you can use the web storage object. But that won't save the layout state. You can save variable values though and use those to do things on load.
You may want to simply pause the rest of the layout and create a sprite or object for your level up screen. Let them pick, assign the values based on their choice to variables, then hide the level up object and unpause the layout...