A projector that can do an 800:1 checkerboard versus a projector that can do a 100:1 checkerboard will show visual improvements in other images; but the checkerboard itself will look about the same.
So the 8X8 checkerboard test is a useful measure even if you can't see the difference yourself in the actual checkerboard shown. The problem with Checkerboard testing is that it requires a near perfect room or for the screen to be covered with black velvet (the later is sometimes called the Putman method)
To actually see the difference that an 800:1 ANSI projector can achieve versus a 100:1, you need to use an image that doesn't throw so much light on the screen. About two years ago, I created a very simple image to show the difference. It is a 128x72 white pixel square in a 1280X720 black image (it is thus 1% white). I called it the "AVS Contrast Test"
compared to a completely black image: http://mrwigggles.250free.com/1280_black.jpg
, you will see a big difference in how much light spill that little square makes. And with these images you can visually see the difference between an ANSI 800:1 projector and a 100:1 projector which might have been invisible in the actual ANSI test.
This simple image was mainly meant for visually spoting differences but you could measure with it as well. Take a reading in the center of the top left white square and then in bottom right corner and you will get an "AVS Contrast Ratio"
for your set-up . (I say "set-up" and not "projector" because some of your result will be based on your room.) A good "set-up" should do 800:1 or greater on this test. If you get less than 400:1, you might want to consider changing projectors or painting your walls to a darker color (or if you forgot to turn the room lights completely off, that might help.)
There might be better tests out there, but it is important to always use black and white in any hypothetical test image. "Dark Gray" squares or dots might seem like a better choice but you don't know how the projector's gamma curve is going to handle it. Also this image is a torture test for auto-iris projectors, the projector can't close the iris to improve the black without white square going down as well and thus reducing the ratio.
It's a stupid simple image test, but it works well.