Quite the nice little application you've got here! Certainly nice to have something to help people display their comics in a simple and intuitive page flip format, and I had no problem following the instructions from cute widdle Bando to do a sample upload (though some of the instructions could stand to be spaced out a bit more so it's not just a big wall of text, such as putting the instruction to unzip the file for personal webpage uploads in a separate paragraph so users don't get confused as they should keep it as a zip for newgrounds uploads).
If I were to have some feedback, I'd say that the viewer is a bit too minimalist for its own good and while it'd be nice to have the option to view just the image with no clutter as it does now, I'd love if there were some additions such as:
It'd be nice if, when you hover over the right side of the page, a right arrow would pop-up to indicate that you'll flip to the next page if you click, and vice versa for the left side: it would make it less confusing as to what action is about to happen.
I feel like you should allow someone to press anywhere on the side of the screen to flip the page, instead of being constrained to only clicking directly on the sides of the image itself.
Would love if there were more utilities for viewing the page, such as being able to click on a magnifying glass to zoom in/out, or being able to choose whether to view pages through a fit width, fit height, original size, and so on.
Would love if there were more options for viewing pages, like maybe a gallery view where you can see all the pages as thumbnails to click on, or a dropdown where you can select a number page to go to, and so on.
I could go on with other additions that'd be great for different formats such as when you want the option for double-spreads or vertical comics, but I'll cut it off there since I could go on and on. Essentially the viewer is nice, but it is incredibly barebones and while that's nice for a minimalist impression and perfectly fine, it does make it a bit lackluster. It's still a nice gizmo though that I hope helps some people publish their comics in nice ways!
As a side note, I just wanted to say that I found the credits on the bottom page very amusing: reminded me of those hacked in rom credits you can see around, haha!