Easy Interface with existing codebase - HTML5 / JavaScript

So I need a simple interface that can work with some pre-existing code. Someone has already made a javascript implementation of what I want done, but the method to interact with it is not how I need it. This is where you come in. The github code, not mine: [login to view URL] A demonstration of it running, also not mine: [login to view URL] From what I can tell from the code, it pulls in tile data raw from the SNES game Earthbound, which is defined in src/rom/[login to view URL], reads the tile data as well as Palette, Movement, and Effects. It then puts this tile data into a bitmap, modifies it, and puts it on a HTML5 canvas object. It does this with two different tile datas, and overlays them. There also seems to be some ability to change the frame delay. I would like the ability to interface with this engine where I can input two indexed-color PNGs (located on the server), palette files (also located on the server in .pal format), and specify the animation for each of the two layers, and it will edit a specified canvas object of arbitrary height and width (although this will almost always be 600 px wide by 450 px tall) to output a similar effect. The engine seems to have the ability to only have one image instead of two as well: this is when the second layer is set to 0. I'd like the same kind of functionality. Again, I need some very simple way for me to interface with this pre-existing engine that doesn't involve the SNES tile objects, so I can use this with arbitrary images. I want it to animate a canvas object as its function, like what this github codebase does. I can provide indexed-color PNG images and palette files if you need them to help develop this interface. I can answer any questions.