reduce APK file size

You could reduce max size to smaller than 1024, use jpgs instead of pngs, could also try 16 bits instead of compressed. That's about all you can do as you have 100mb of images so your actual app is only about 24 mb.

It does not matter which size or compression level is your image when you put it in the project, it only matters how that image is imported. So the first rule is: never use lossy compression (jpg) for your source images, as soon as you only will add artifacts to the image, without any advantage. 1MB for one 1024x1024 png image is not that much. I think that anyway 1024 is rather a big format for a cell phone, you can reduce the import size to 512. The second thing you can do is to import it as Crunched instead of Compressed, that should generate a lossy version and hence reduce the size. If that doesn't fit, the only other possible solution is to load the images from an online server.