I agree, this interface requires improvement in UI. But there is no harm with keeping images in the resource library even if they are not mapped to anywhere. It it just a repository.
Fastest way to inspect HTML, CSS and Javascript is to use Firebug with Fire Fox browser. You can quickly locate CSS class, file location, etc. Not to mention edit n the fly.
You can use any image software on your computer to format, optimize and resize your images.
If really necessary, extension can be created to format uploaded images, but they way browsers work large image will be still uploaded first to the server before resizing.
Why do you want your bandwidth and server work for you instead of your computer?
I think the key is something specific to extension store. It is automaticaly generated on purchase.
From what I understood, there are no spcific requiremet how you can create template. It can be in /storefront/view/ or it can be as extension.
If you make it as extension you will make it better in case of upgrades and you can offer additional setting along with extensions. Also you can habudle of extensions togethere with the template.
If you put it to /storefront/view/ it is purely skin and there is no update process in there
If you want to sell your template in algozone marketplace, it has to be an extension.
Can not see what can cause this without futher investigation. Since you operate locally on XAMPP it will be hard for us to check. I tried XAMPP set up and it works fine