I found this image to be great for gamma and brightness.
I'm posting three pictures. The original, one with too much gamma/brightness, and one too dark.
In the original (first post, you shouldn't see her left eye (just on the verge of being visible) but should see the strand of hair on the left side of her face. You should also just barely make out the shape of the left side of her face.
The second picture shows the hidden features of the picture, her left eye and a lot more hair.
The last darkened picture results in most of heir hair being too dark to see.
Kind if a nice picture test (instead of color bars, etc) to see if you gamma/brightness is set well. Interesting note. On the Dell 2405, if I look at an angle, I can make out her left eye but with the Acer 24" inch, I can't. I think that's actually a telling sign that the newer Acer handles viewing angles a little better as the picture remains unchanged with extreme viewing angles.
Image one: Original:
Image two: washed out to reveal details
Image three: darkened
