Possible to have multiple "projects"?

[celeritydesign]

I'm not sure if there is a good solution to this problem, so I will outline what I'm trying to do and the problem I'm having...

I am working on an 8px spritesheet and tilemap for background, but for my game sprites, I am obviously using 16px mode. Your tools have really cool offline functionality and use browser storage, so even if my laptop dies I can go back to the page and my background and spritesheet is still there. The problem is now that I need a separate 16px spritesheet, it has obviously overwritten the browser store, so I've lost my old work. I know I can reload the files, but would it be possible to work in two separate browser tabs, allowing me to reference my background level whilst working on sprites etc, as well as still having the benefits of browser storage for each tab? Maybe "save this project as..." and then have a dropdown allowing the user to select between their different projects?

Out of interest, how do you work using tile sprites and game sprites at the same time?