Note: Some themes may be found here as well. The ones listed here though are verified as working with my update script. Others in that topic may work but I cannot vouch for all of them.
Another Note: Tons more found here (read site for instructions and app)
How To Apply Themes:
All my script does is replace image files so if ever it does not work, you can just manually place the files back into /System/Library/CoreServices/Dock.app/Contents/Resources. The script is set to copy everything in the current directory (in terminal) to this location. Therefor, to get the originals back or use your own images, just have them named correctly and have terminal's directory set to their's (this is done by just typing "cd " with a space after and then dragging in the folder in which the images are) and then typing "bash " (with a space) and dragging in my 'updatedock' script (Attached to topic below).
How To Change To 2D Dock (on bottom)
Open Terminal and paste in this code (change 'YES' to 'NO' to get 3D back):
defaults write com.apple.dock no-glass -boolean YES; killall Dock
djh816's themes (5 theme pack with download link at bottom):
(Backup Originals Also Included)
Woodgrain dock (with no reflections):
No-Reflection Indicators (no preview):
108 Dock Pack (no preview):
EDIT: Fixed indicator images in backup (again. sorry x2). Keep them coming guys. I will continually update.