What's the magic formulae for good background texturing?

The textures on balance are 37% transparent and are greyscale from the original color ones... and it significantly changes the colors, and makes it all hard to see.

But some boards here have really nice background textures that don't do that (change the colors)

What's the secret?

Changing the colors in the designer so that you end up with the color you want in the end.  I take my nearly transparent texture image and add a layer below it of the color that I want and keep playing with the RGB until I get what I want then I take that Hex number and put it into the designer.  It's hit and miss but it's how I get what I want.

Looking at this board image it looks like all of the texture pie slices are indeed greyscale but that does not mean that they all have the same amount of white pixels.  The tecture used in the Heaven slice has a lot more white in it.  This would change the white balance of the fills that show through it and change the observed color.

It is like looking through a window with chicken wire across it vs a window with silver screen on it. 

Two ideas:

You could take the Heaven and Lake and maybe the Earth pies and make them even more transparent than the other pie slices.  This would allow more fill color through until thay were closer to the other spaces. 
Create a fill layer with one color in all of the spaces (red works well).  Then adjust the transparency of each slice until you get an even look.

Or you could choose one consistant texture for all of the filled spaces.  You could still leave the unique textures on the frame work but have one texture in all of the fill spaces.  That way every space would look exactly the same.

ratsy, if you're looking for advice regarding a specific board (Raptor seems to think he knows which board you're talking about), it would be nice if you could post a link.

One huge part... make sure the transparent part over the fill is black and white.

Also, I would select the colors you want in your editing program, then go to colors to identify the Hexcode, then you can know what the color will look like before testing.

This is super good advice and I appreciate it. Thanks guys. Raptor is talking about my board "balance" which I am sure is giving him a headache playing it (it is for us all) but I was really looking general advice. There are some beautiful boards out there, and I'm having some trouble getting it just right - comparatively anyway....

Take a look if you like:
http://www.wargear.net/games/view/149377
or
http://www.wargear.net/boards/view/3649