You can get a variety of image loaders and some of them feature a percentage complete type of loader.
Unless you set out to protect your images from being cached by a visitors browser though, once they have been loaded into their browser once, subsequent use of the same image on more pages will pull it from their cache and not from your site anyway, so I'm not sure where you're going with this.
It's one of the fundamentals of using image content in your web. If an image repeats over more than one page the last thing you want to do is load it every time someone requests a page, so you design it to load from cache after it has been loaded for the first time.
An easy example is if your site had a graphic for a banner over the top of the page. If your banner if called banner.jpg, as long as you use the same image file for every page, once I see it for the first time in my browser, every other page that I visit on your site pulls that image from my browser cache rather than reloading it from your web server.
For some image loader scripts, try click here and click here which should get you started.