Question about reduce file size when creating sprite(2D) animations

Hey All:

I am currently working on a comic book app targeting mobile platforms. I am using png/jpg files convert them into sprite animations. The problem is the file is too large, I already converted them to max size to 512 and format is 16 bits, the size is still around 0.5mb per image, I wonder if there is a way compress file more? I am thinking about if I could store those images somewhere else or I should use other method to create animations.

Thanks!

Check the Image itself from were it was exported . Say while using .psd file you get lot of setting in photoshop to lower the size.