You'll notice how difficult it is to see the Dock background against my beautiful automobile wallpaper.
Step 1: Locating the System Folder.
This is convenient for certain modifications we might want to make to the appearance.
So, let's start off by locating Dock.app
It's not as simple as a Spotlight search, mind you. You'll want to open up a Finder window, and navigate to your startup disk. (If you don't know what this is, you probably left the name as "Macintosh HD") You'll see a folder called "System". Go ahead and open that up.
Step 2: Open the Contents of Dock.app
Step 3: Find Your Dock Image, Change It Up.
Anyway, you'll observe that there are 3 images entitled scurve-something within the folder "Resources". Based on the quantity of icon content in your Dock, you'll need to select one of these. Sm means small, m means medium, l means large, and xl means extra large. Once you determine which one is for you, you need to copy it twice to a backup location, wherever you choose really. Just a place that you can keep a backup copy in case you want to change it back. So once you have your 2 copies, open one of them in your favorite image editor. I used iPhoto just to edit the tint, but you could use GIMP or Photoshop if you wanted. When you're done editing that, replace the original with the edited one in the Contents window. You're done! When you reboot your Mac, or kill the Dock, you should see your changes! Here's what I did to mine.