In this demo I use a 42x32 red square image file (84 bytes), scale the picture 2000%. (42px * 2000% = 840px, 32px * 2000% = 640)
Standard Screen Width is 816, Screen Height is 624
Also set opacity to 120 to give an translucent overlay.
The small dimensions of the source image should help with any lag issue & reduce file size.
I use "this.changePictureLayer(pictureId, layer)", this does not bind the picture to the map, it simply sets the picture behind the characters. This way the tint will always be locked to the screen rather than the map.
You could also just use the image how ever needed really, play around and see what suits your needs. It doesn't have to be a solid color either... I just did that for this demo.
Demo was inspired by this post:
No credit needed to myself, credit Tor Damian if you use the plugin.